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Gemme, Minerali, materiali lapidei e termini tecnici

Questo piccolo glossario vuole fornire ai visitatori , amanti delle gemme, dei gioielli , un veloce mezzo di consultazione per chiarire qualche piccolo dubbio : abbiamo cercato di ridurre al minimo la parte più puramente scientifica, tentando di fornire quelle conoscenze empiriche che permettono di riconoscere una specie gemmologica. Ovviamente, è inutile dire che, cercheremo di tenerlo sempre aggiornato e vi saremo grati per qualsiasi segnalazione di errori e carenze.
Il testo in colore verdino si riferisce a consigli sulla cura e la conservazione delle gemme.
Il testo in colore violetto riporta le piu comuni imitazioni e falsificazione delle gemme, nonchè i nomi commerciali fuorvianti e i prodotti che imitano o simulano le gemme.

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GAHNITE

[rara gemma da collezione]
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GEM SILICA

[rara gemma da collezione]
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Garnet > GRANATO



GASPEITE

[Considerata una rarissima varietá Verde della TURCHESE, in realtà una spoecie mineralogica distinta.] Gaspeite ( (Ni,Mg,Fe)CO3 ) Koivula, Kammerling & Fritsch (1994, p,126) cabochons, beads, etc. are made from a massive yellow-green variety of this mineral, first found on the Gaspé Peninsula, Québec, Canada; also found at, for example, Kambalda and Widgie Mooltha, Western Australia – this latter material is commonly marketed as "Allura."

Gemma (en: Gemstone)

Minerale, composto organico o biomineralizzazione che possiede sufficiente bellezza , purezza e durabilità per essere usato in gioielleria.

Gemmologia (en: gemmology)

Scienza dello studio e del riconoscimento dei materiali di origine minerale, vegetale e animale, usabili in gioielleria e ornamentazione.

GENTHELVITE


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Giacimento (en: Deposit, Ore)

Concentrazione naturale di minerali utili, sfruttabile economicamente.

Giacimento alluvionale (en: alluvional deposit)

Arricchimento naturale di minerali utili mediante trasporto idrico.

Giacimento magmatico (en: magmatic deposit)

Arricchimento naturale di minerali utili legato direttamente a una massa magmatica della crosta terrestre.

Giacimento metamorfico (en: metamorphic deposit)

Arricchimento naturale di minerali utili legato al metamorfismo di rocce e minerali preesistenti.

Giacimento primario (en: primary deposit)

Accumulo naturale di minerali utili nel posto della loro prima deposizione.

Giacimento secondario (en: secondary deposit)

Accumulo naturale di minerali utili, lontano dalla roccia madre, dalla quale sono stati asportati, a seguito di alterazioni, e poi ridepositati.

Giacimento sedimentario (en: sedimentary deposit)

Formazione naturale contenente una concentrazione di minerali utili formati a seguito di processi chimici e/o fisici in sedimenti inorganici o organici.

GIACINTO (Zircone)

Antico nome dello ZIRCONE usato soprattutto nelle arti alchemiche e magiche, talvolta ancora usato in gemmologia.

GIADA (en. Jade)


THE JADES ( Fr: jade / de : Nierenstein , Beilstein / Nrw : jade ) THE JADES A. Jade. "Trumpeters Dance" (ca. 33 x 30 x X 17 cm) sculpted from green and black nephrite from British Columbia and white jadeite from Myanmar (formerly Burma). (© photo courtesy Lyle Sopel Studio Inc. of Vancouver, British Columbia, Canada, www.sopel.com) B. Jade. Pieces as follows: center, carved jadeite cabochon (longer axis - 1 cm); right side, nephrite carving with pointed top; clockwise from nephrite earring (New Zealand); nephrite Buddha; jadeite cabochon; nephrite brooch (New Zealand); and nephrite carved cabochon. (© photo by Dick Dietrich) C. Jade simulant. Alabaster carving (height - 24 cm) dyed green to resemble jade. R.V. Dietrich collection. (© photo by Dick Dietrich) DESCRIPTION: Two different gemrocks are designated JADE: One consists wholly or largely of the pyroxene jadeite; the other consists wholly or largely of the amphibole nephrite of the tremolite-actinolite series. Properties of these two rocks that are similar follow: Color - diverse shades of green (ranging from relatively dark spinach green to light apple green), creamy off-white, mauve, pink, reddish, orangish, yellowish, bluish lavender, lavender, tan, brown, gray and black; with exceptions, jadeite is vari-colored whereas much nephrite is spinach green, white or black; although some jade, as fashioned, exhibits only one highly saturated virtually homogeneous color, commonly it comprises unevenly distributed zones of different shades of the same color or a combination of those shades along with diverse shades of one or more of the other colors -- this gives pieces fashioned from it overall mottled appearances. Light transmission - subtransparent to subtranslucent in thin pieces Luster - waxy to softly glossy; many jades appear soft toned. Breakage - subconchoidal to irregular fracture Miscellaneous - Both jades are unusually tough and when polished and commonly feel especially smooth. Additional properties, such as hardness and specific gravity, are given in the JADEITE andNEPHRITE entries. OTHER NAMES: Jade has been given several names, especially in the past. These names have been based on such diverse things as color, toughness or hardness, time (e.g., the period of a Chinese dynasty during which carvings were fashioned from the given jade), place where the jade was recovered or marketed, and use -- e.g., by whom or to fill what primary function. Many of these names, of which a large number have Chinese or Central American Indian origins, are given in gemological dictionaries --e.g., the "Dictionary of gems and gemology . . ." (GIA, 1974). A few examples follow: Color:
  • Blood red jade (Man jade) - self explanatory, though some so-designated jade is pink rather than blood red.
  • Mutton fat jade - clear off-white to yellowish, usually nephrite jade.
  • In addition to using the common colors as adjectives, diverse hues of jade have been compared to many things and given those names as adjectives, especially by the Chinese: While making a rapid-fire scan of the "Dictionary of gems and gemology ... " (GIA, 1974), I saw the following: antelope jade, apple jade, betel nut jade, camphor jade, chalk jade, chestnut jade, coal jade, coral jade, date stone jade, duck bone jade, egg jade, fish belly jade, fruit flesh jade, ice jade, ivory jade, kingfisher jade, lilac jade, lime jade, quicksilver jade, sandalwood jade, and spinach .... Today, common color adjectives -- e.g., blue, lavendar, black and white -- are used most often to describe the color of jade; however, additional adjectives also continue to be used allusively -- e.g., brown sugar jade, mutton(or sheep) fat jade, tiger's skin ...(Fuguan, 1979).
  • Pattern:
  • Morning dew jade - greenish jade sprinkled with glistening specks.
  • Leopard jade - spotted jade with its pattern roughly resembling that of leopards' coats.
  • Texture:
  • Chicken bone jade - along with its off-white color, this jade exhibits a yellowish discoloration.
  • Soft jade -- the "soft feel" of this jade -- typically a mutton fat jade -- is at least in part a manifestation of its texture.
  • Time:
  • Han Yü - jade fashioned during the Han dynasty.
  • Place:
  • Burma (or Burmese) jade - jadeite from mines in Mogaung, Upper Burma (now Myanmar).
  • Shanghai jade - jade marketed at Shanghai.
  • Tangawaite - nephritic jade from New Zealand.
  • Antique Soocho Jade - "Antique Soocho Jade" is actually a multi-colored jade gemstone. This multi-colored jade ranges in color from black, brown, and rust to blue-green, green, and white. Most jade is cut in China, Taiwan, and Hong Kong.
  • Use (by whom):
  • Maori stone - New Zealand nephrite jade used by the Maori.
  • Mayaite - diopside-bearing jadeite jade from Central America used by the Mayas.
  • Use (for whom):
  • Imperial jade - this designation, still used, was applied originally only to the highest quality translucent emerald-green jade fashioned into articles for imperial monarchs.
  • Use (for what):
  • Tomb jade - jade customarily buried by the Chinese with their dead; it is typically opaque reddish, yellowish or brownish, very likely because of oxidation suffered during burial. (I have been unable to find out if this is or is not the same jade that Fuquan (1979) reported as follows: "During the Han dynasty (221 B.C. - 220 A.D.), the bodies of members of the royal family wore clothing made of small jade tablets strung together with gold, silver, or bronze thread when buried... [--for those who wonder about the weight of such burial garments, Fuquan adds, though not directly referring to the "tablets",] During the Qing dynasty (1644-1911), many jade carvings were so finely done that in places they were as thin as cicada wings and as slender as hairspring."
  • A few frequently used adjectival designations now in vogue, which are usually used for jadeitic versus nephritic jade, are given in those entries. USES: Jade has been fashioned into a large number of extremely diverse items used in jewelry and into both functional and ornamental pieces. A few examples follow: bangles, beads, brooches, buckles, buttons, earrings, hair-pins, hololiths, masks, pendants, rings, and stick pins; diverse carvings, many of which exhibit almost unbelievably intricate details (e.g., animals, birds, fish, gods, humans and insects); vessels (e.g., bowls, cups, incense burners and vases); both blades (etc.) and handles for cutlery; tools and weapons such as axes, knives and spearheads; congs; discs; seals; snuff bottles; amulets; masks; and fondling pieces. Some jade pieces -- e.g., carved bowls -- have gold inlay and/or gemstones. Fine photographs of many jade pieces are shown in several widely available publications (e.g., "Jade," edited by Keverne, 1992) as well as in the famous, albeit rare (edition was limited to 100 copies), Investigations and Studies in Jade, which describes the famous Bishop collection in New York's Metropolitan Museum of Art -- see Bishop Collection in Appendix C. -- In L.J. Spencer's words (1971), this publication is "perhaps the most remarkable book ever produced . . . [--] two folio volumes [that] weigh 125 lb. . . . produced regardless of expense, and [including] . . . numerous coloured plates [that] are veritable works of art." OCCURRENCES: See JADEITE and NEPHRITE entries. NOTEWORTHY LOCALITIES: See Ward, 1999; See also JADEITE and NEPHRITE entries. REMARKS: The English name jade is apparently derived from the Spanish piedra de ijada, which means loin stone; in turn, that designation appears to have arisen from the belief that jade had the power to cure kidney ailments -- it is a matter of record that powdered jade was once prescribed as a cure for kidney diseases. The name nephrite, being derived from lapis nephriticus (kidney stone), is of similar origin. . Some gemstones, carvings etc. of both jadeite and nephrite have been dyed or otherwise treated to change or enhance their color(s). The dye of some of these jades is easily discerned because concentrations are commonly irregular because of porosity/permeability differences in the original jade and concentrations of dyes are rarther obvious along fractures; unfortunately, however, for some jades -- e.g., most lavendar jade -- the dye is not easily detected. Another check for dye, which is used on occasion, is to rub the jade in question with a piece of cotton soaked with, for example, acetone to see if the cotton becomes discolored. In addition to dyeing, both jadeite and nephrite jade may have their colors bleached or enhanced by heat or irradiation. A common followup for jade that has been bleached is to impregnate it with, for example, some polymer in order to make it more stable. Yet another common treatment is waxing (e.g., with paraffin) of jade to improve its luster. Etc.,. . . etc. -- Along this line, although no classification relating to these diverse treatments is accepted universally, several experts and dealers tend to go along with the following: Type A - untreated; Type B - bleached and impregnated by polymers; Type C -dyed. One treatment of certain jades leads to what has been called "magnetite jade." Schumann (1977, p.206) describes this jade as an "opaque black jade, electrolytically plated with gold . . . ." More recently, in her statement about jades from northern California, R.A. McArthur extends the description of this treatment and clarifies the results: "There is . . . a black jade with puffs of magnetite crystals in it. They polish the jade, then electroplate [it] with gold. Just the magnetite crystals pick up the gold. It is quite stunning." -- See the following web site: www.ganoksin.com/orchid/archive/200105/msg00258.htm Some jades in jewelry have foil backings; others are composites -- i.e., doublets or triplets. A caution -- jade should be kept away from intense heat and acids. Jade, perhaps the most widely cherished gemrock, early gained its high standing in China, Central America, and New Zealand. As noted by Smith and Phillips (1962), "According to the Chinese, jade is the prototype of all gems, and unites in itself the five cardinal virtues: Jin (charity), Gi (modesty), Yu (courage), Ketsu (justice) and Chi (wisdom). When powdered and mixed with water, it is supposed by them to be a powerful remedy for all kinds of internal disorders, to strengthen the frame and prevent fatigue, to prolong life, and, if taken in sufficient quantity just before death, to prevent decomposition." In addition, as the frequently quoted statement of Richard Gump (1962), states, [Jade] "has a 'certain something' that made a Chinese emperor offer 15 cities for a jade carving he could hold in one hand; that made Montezuma smile when he heard that Cortes was interested only in gold, since Montezuma's most precious possession was jade. That caused men of civilizations oceans and centuries apart to believe it to be the stone of immortality. That made some men ... speak through it to their gods, and still others spend years carving a single object from it." In the past, several colors and hues of jade have been attributed different meanings or uses -- for example, in ancient China, bluish, yellow, green, red, white and black jades were related to the heavens, the earth, east, south, west and north, respectively. Also, jade has probably had more mystical qualities attributed to it than any other gem material. Indeed, the literature about jade gives examples ranging, in my opinion, from the proverbial ridiculous to the sublime. As a "jack-leg" musician I was particularly interested when I read "The tone of bells made of jade is repeatedly the subject of enthusiastic praise by poets of China and other lands" (unattributed Gems & Gemology, 1934, 81). Along this line, the following information is given by Kunz (1913): "A series of oblong pieces of jade, of the same length width, usually about 1.8 feet long and 1.35 feet wide, and numbering from 12 to 24, constitute a chime, the difference in the notes emitted by the material when sharply struck depending upon the varying thickness of the separate pieces. ... [and] the 'stone chime' used in court and religious ceremonials, is composed of 16 undecorated stones, while a series known as the singers' chime consists of from 12 to 24 pieces carved into fantastic shapes." Jade was chosen as the Mothers' Day gem by the American Gem Society in 1934. According to Bell (1934) reasons for this choice (over, for example, amethyst -- questioned as "more suitable for a grand-mother? Is it not associated with lavender and old lace?") were: [It is] "a gem which could be procured in a wide price range -- one which could be used as a ring stone, for earrings, clips, brooches, beads, as a color accent to costumes. The smarter and deeper green shades of Jade can be selected for the younger mother -- the white, lighter green and lavendar shades for the older mother. ... it offers opportunities for successive gifts during the years. [and] The Chinese rank Jade above all precious stones and they believe it unites in itself the five cardinal virtues – Charity (which is love), Modesty, Courage, Justice, and Wisdom. These virtues are surely the attributes of Mother." Jade, not otherwise defined, was named the state gemstone of Alaska. The "Emblem [Order?] of the Blue Jade" has been referred to as China's highest honor; it received widespread attention in the United States because of a book that reported its being awarded to Minnie Vautrin, a native of Illinois, who as a missionary in China is said to have been responsible for having saved as many as 10,000 people from the marauding Japanese army when it invaded China in 1937; Vautrin's medal is now in the collection of the Illinois State Museum in Springfield, Illinois. SIMULANTS: Since time immemorial, possession of something fashioned from jade has been widely desired. Consequently, because of its relative rarity, many materials that either resemble jade or could be made to resemble jade have gained their places in the marketplace as jade substitutes. The following list gives those compiled by Jill Walker for the book "Jade," edited by Keverne (1992) along with noteworthy additions of which I have become aware. A few of these are illustrated in the book about jadeite by Ou Yang (2003). One or more relatively easy ways to distinguish each of the simulants from jade by mascroscopic examination or some simple test is given in square brackets ([ ]) following most of the listed simulants. Along this line, however, it seems only prudent to note that some of these materials are not homogeneous, so their properties may differ markedly from specimen to specimen as well as from one to another part of individual specimens. Some people have learned how to distinguish jade from its simulants and even jadeite from nephrite, by merely examining specimens -- such expertise reflects their experiences over relatively long periods of time and involves acute observational powers and exceptionally fine memories of interdependent properties such as luster, texture, character of fracture surfaces, presence or lack of inclusions, feel of polished surfaces etc. Most of these experts, however, willingly -- and prudently -- admit that truly positive identifications may require the use of relatively sophisticated equipment. Therefore, anyone who wants a reliable identification of a jade piece should seek the aid of an expert who has both the experience and the availability of the appropriate equipment.
      Le più frequenti imitazioni della Giada :
    • Agate - The designation "Japanese jade" has been applied to "an opaque, nonvitreous, milky-white agate with spinach-green splotches" (Messchært, 1966-67). - [inferior specific gravity].
    • Agalmatolite - name frequently applied to rocks made up largely of "pinite" (i.e., micro- or cryptocrystalline muscovite), pyrophyllite, ... See Appendix A. - [inferior hardness and specific gravity].
    • Agate - "an opaque, nonvitreous, milky-white agate with spinach-green splotches" (Messchært, 1966-67). - [inferior specific gravity]
    • Alabaster - see ALABASTER entry. - [inferior specific gravity].
    • Alaska jade - see pectolite rock.
    • Albite jade (also called Water Mill Stone) - "albite, with small amounts of barium feldspar, pyroxene and amphibole minerals" (Ou Yang, 2003); the material Crowningshield (1957, p.36) described as "a combination of white albite feldspar and green actinolite" seems also to belong here. - [lower S.G; And, most of it has been fashioned into bangles, which do not ring like jade bangles (ibid.).].
    • Amazonite (amazon stone) - sometimes referred to as Amazon jade or Colorado jade; see Feldspar.
    • American jade - see Vesuvianite.
    • Andes jade - name used in marketing a serpentinite -- shown to consist largely of antigorite and lizardite, along with magnesite and minor magnetite and garnets -- from central-western Argentina (Laurs, 2007).
    • Andradite - see Garnet.
    • Antigorite - see Serpentine.
    • Aragonite dyed, for example, green. - [inferior hardness and effervesces with dilute HCl].
    • Aventurine quartz, dyed purple - recorded by Crowningshield (1960, p.51) as "purple beads sold as purple jade ... [but] not too attractive and, under any name, would not have had much value." -- see Quartz/Quartzite.
    • Aventurine quartz/quartzite (Henan jade, Indian jade, silver jade) - see Quartz/Quartzite.
    • Beryl - nontransparent green varieties. - [lower specific gravity].
    • Black jade - some material so-labeled has been determined to be serpentine (Liddicoat, 1965, p.284). - [inferior hardness]. See also remarks under Omphacite.
    • Bonamite - see Smithsonite.
    • Bowenite - see Serpentine.
    • Calcite (especially onyx marble -- see under TRAVERTINE entry) - dyed (in some cases, selectively) green, etc. This simulant is sometimes called by such misnomers as Imperial Mexican jade, Mexican jade or Tecali. - [effervesces with dilute HCl; inferior hardness].
    • Californite (or California jade) - see Vesuvianite jade.
    • Ceramics - polished ceramics of appropriate colors. - [Appearance should suffice.].
    • Chalcedony: especially chrysoprase, plasma or prase varieties - e.g., Australian jade, Nanyang jade, and Queensland jade. - [lower specific gravity].
    • other varieties (dyed) - [as preceding listing].
    • see also Yü on this list.
    • Chalchihuitl - this Aztec word for green stone is applied widely in Mexico to jade, BUT also to, for example, carvings made of other green gemrocks -- e.g., marble, serpentine, smithsonite, and turquoise.
    • Chlorite - see Serpentine.
    • Chrysoprase - see Chalcedony.
    • Cordierite - two carvings orginally thought to be gray jadeite were determined to be cordierite (Liddicoat, 1967-1968, p.249). - [lower specific gravity and superior hardness].
    • Dianite - name used, especially in Russia, for the material listed here as Siberian blue nephrite (Johnson et al., 2000, p.66-67).
    • Diopside-rich rock from Central America - perhaps this should not be considered to be a substitute in that diopside is a pyroxene with a composition close to that of jadeite. See also Omphacite, below. An apparently similar rock that consists largely of chrome diopside plus lesser amounts of chromite, pectolite and uvarovite garnet, from Hokkaido, Japan has been called hidaka jade.
    • Dolostone - fine grained and dyed. - [ inferior hardness; Dolomite effervesces, albeit slowly, when attacked by dilute HCl.].
    • Emerald - that used as a jade substitute is typically translucent to subtranslucent and not of the quality used for transparent emerald gemstones - [inferior specific gravity].
    • Feldspar (amazonite variety of microcline) - Amazon jade and Colorado jade. - [Appearance suffices.].
    • Fibrolite - see Sillimanite.
    • Fluorite - "Crudely worked ornaments of green fluorspar, possibly a cheap substitute for jade, have been found in China" (Ford, 1955). - [inferior hardness (H. 4)].
    • Garnet:
    • massive green (and several other colors -- see Webster, 1963, p.35) grossular - e.g., Garnet jade, South African jade, Transvaal jade and White jade - [hardness is greater than that of jade].
    • dark green andradite - Transvaal nephrite. - [Hardness is greater than that of jade.].
    • Ghost jade - a relatively coarse-grained (and, for this reason not considered jade), largely nephrite rock from western Nevada (Johnson et al. , 2000, p.67) - [large grainsize]. See AMPHIBOLE -RICH ROCKS entry.
    • Gibbsite dyed green - this simulant is recorded by Hurwit in Moses et al.(2001). - [inferior hardness and lower specific gravity].
    • ***Glass, colored appropriately (usually some shade of green) and manufactured to be translucent - marketed as jade under such names as pate de riz. - [inferior hardness; common presence of gas bubbles or swirled striae, which can sometimes be seen by using only a handlens; vitreous rather than waxy or greasy luster].
    • Also devitrified glass including Iimori stone or Meta-jade - apparently a partially devitrified apatite-composition glass (see Walker and Mayerson in Moses et al., 2001). - [inferior hardness and conchoidal fracture].
    • See also volcanic ash on this list.
    • Goodletite - see GOODLETITE entry.
    • Greenland (Grønlandite) - a green to bluish green quartzite, the color of which is dependent upon the presence of fuchsite (a green, chromium-bearing mica) from the Nuuk (Godthåbsfjord) area of Greenland. - [superior hardness.] See also QUARTZITE entry.
    • Greenstone - this term is widely applied to several diverse rocks and a few minerals (e.g., metamorphosed basalt and chlorastrolite), most of which do not have characteristics that make them lilkely substitutes for jade. However, one so-designated rock, from the Langhko district, Shan State, Myanmar (formerly Burma), has apparently been so-used; it consists of "radiating aggregates of green-to-yellow long, prismatic fibrous crystals [-- apparently tremolite-actinolite --] imbedded in a fine- to medium-grained limestone" with diopside and quartz as sporadic minor constituents (Hliang, 1992) - [Appearance suffices.].
    • Grossular - see Garnet.
    • Grossular-vesuvianite (recorded as grossularite-idocrase) - two so-to-speak paired carvings, one with grossular predominant, the other with vesuvianite predominant are illustrated by Crowningshield (1967, p. 137-138). - see Garnet.
    • Gypsum (massive alabaster, light green) - Oriental alabaster - [inferior hardness].
    • Hidaka jade - see Diopside-rich rock ...
    • Hydrogrossular - diversely colored polycrystalline, predominantly hydrogrossular masses have been carved and made into beads that have been marketed as rare jade (e.g.,McClure & Kammerling, 1992, p.264 and Hurwit in Moses, Reinitz & McClure, 2000, p.63-64). - [higher specific gravity].
    • Idocrase - see Vesuvianite.
    • Inky jadeite jade - see Omphacite.
    • Ivory - Walrus ivory is recorded (Ahrens, ca. 1986, p. 24) to have been used to "imitate" imperial jade. - [Close examination should suffice.].
    • Jade matrix (also called snowflake jade) - a rock consisting largely of a greenish amphibole, probably tremolite, plus an off-white feldspar, probably albite. - [Appearance suffices.].
    • Jadeolite - see Syenite.
    • Jasper (naturally or stained green) - e.g., Hsui yen, Jasper jade, Oregon jade and Swiss jade. - [Texture is typically relatively coarse compared to that of jade; specific gravity is less than that of jade.].
    • Kosmochlor (formerly called ureyite) - some jadeitic jade from, for example, Myanmar (formerly Burma) is made up of relatively large percentages of the pyroxene kosmochlor; some gemologists -- e.g., Htein and Naing (1994) - have advocated applying the name jade, with no modifiers, to these rocks. See MAW-SIT-SIT entry.
    • Kyet Tayoe - Una varietà verde-mela relativamente chiara di Maw-sit-sit. Cfr Mawvsit sit.
    • Longxi jade - Serpentinite o o roccia a Tremolite dal Sichuan in China.
    • Silver Peak jade. - Malachite[inferior hardness, effervesces with dilute HCl].
    • Malaysian jade - > Quarzite.
    • Manchurian jade - > Talco.
    • Marmo (solitamente tinto) [dyed Marble]- soprattutto marmo che presentano strutture affini a quelle di certe giade - [minore durezza, effervescente con HCl diluito].
    • Maw-sit-sit (jade-albite, an ill-chosen misnomer). - [multi-mineral makeup can be seen with naked eye in most cases, and with aid of 10x handlens in essentially all cases.]. see MAW-SIT-SIT entry.
    • ***Meta-jade - an Iimori glass. - [see Glass].
    • Metavariscite - [inferior hardness (H. 3-4); lower specific gravity ~2.55; Appearance usually suffices.].
    • Microcline (variety amazonite) - see Feldspar.
    • Mountain jade Coral > Marmo timto e lucidatio
    • Mountain jade Green > Marmo timto e lucidatio
    • Mountain jade white , splendida pietra bianca commercializzata come Giada di montagna o anche onice bianco , che in realtà e un belissimo marmo dolomitico bianchissimo che probabilmente vien anche trattato per conferirgli una lucentezza vestrona e renderlo simile all'onice nero .
    • [[Nephrite has apparently sometimes been represented in the marketplace as jadeite?!?]]
    • Nunderite - brown-spotted green rock consisting of jadeite plus plagioclase feldspar from Nundel, New South Wales, Australia. - [easily seen to be made up of two or more minerals].
    • Omphacite - rocks composed of largely of this pyroxene -- which is closely related to jadeite, diopside and aegirine -- have been used in lieu of jade for carving of such things as masks in Central America for decades; more recently, it has become common, both as smooth pebbles (rough) and fashioned cabochons and small carvings, in Hong Kong and Chinese markets. The Central America material, according to William Foshag (1957), an old friend from the Smithsonian, has been called diopside-jadeite (see also Diopside-rich rock ... listing); the material marketed in Asia as "inky jadeite jade" is described in detail by Mei et al. (2003) as consisting greater than 85 per cent omphacite plus jadeite, kosmochlor, opaque metal oxides and "specks of graphite or possibly a black organic material." This "jade simulant" has been simulated by dark green to nearly black nephrite jade and black, or nearly black, serpentine. - [Omphacite rocks do not really look like any typical jade, but it may be wise, when "black jade" is encountered to have someone who has the appropriate equipment check its refractive indices.].
    • Oregon jade - "1.European misnomer for a variety of green jasper. 2.Massive green grossular rock found in Oregon; term also applied to other green, jadelike rocks, e.g., plasma, found in Oregon and California" (Mitchell, 1985) - [see Garnet and Jasper on this list].
    • Peace Jade - Nuova roccia Chinese composta da una mistura di serpentino (verde più o meno pallido), stichtite (lavanda), e quarzo bianco . These peace jade beads come in tranquil shades of cream and soft green, with an occasional hint of lavender.
    • Pectolite rock - name sometimes used for a tough massive fine grained pale green pectolite-rich rock that somewhat resembles jade. That from the vicinity of Point Barrow, Alaska has sometimes been called Alaska jade - [inferior hardness; decomposed by warm dilute HCl].
    • Pinite - see Agalmatolite.
    • Plasma - see Chalcedony.
    • Prase - see Chalcedony.
    • Prehnite - Japanese jade. - [gelatinizes with HCl].
    • Pseudophite - see Styrian jade.
    • Pyrophyllite - see Agalmatolite
    • Pyroxene jade - see remarks under Omphacite.
    • Quartz/quartzite (green aventurine variety) - has been marketed as imperial yu, Indian jade, Regal jade, and silver jade. These quartz-rich gemstones have been described variously as quartz or quartzite; in my opinion, the most dependable description (Webster, 1949) indicates that at least the one termed Indian jade, is a quartzite with fuchsite inclusions. - [lower specific gravity; conchoidal fracture]. See also Chalcedony and Jasper and QUARTZITE entry.
    • Quartzite dyed green (sometimes marketed as Malaysian jade), pink or yellow OR selectively dyed to resemble moss-in-snow jade. - [same criteria as given for Quartz/quartzite].
    • Queensland jade - a chrysoprase chalcedony. - [see Chalcedony].
    • Red jade - reddish quartzite. - [see Quartz/quartzite].
    • Resin - replicas of hand-carved jade items such as talismans that have been "cast in quality, translucent resin with a jade finish" are advertized in mail order catalogs.
    • Rhodesian jade - see Verite.
    • Saponite and/or talc; several other names --e.g., lardite, lard stone, pagodaite, Honan jade, and Souchow jade -- have been applied to these rocks. - [inferior hardness].
    • Saussurite (also called Dushan jade, jade tenace, Nanyang jade, and Swiss jade) -This alteration product of some basaltic composition igneous rocks, or more particularly to their plagioclase feldspar component, consists largely of albite (sodium-rich plagioclase feldspar) and epidote and/or zoisite (both epidote group minerals) and commonly also includes lesser percentages of calcite and sericitic mica plus or minus one or more of the zeolite group minerals and/or prehnite. Some saussurite appears macroscopically homogeneous -- indeed it was once considered to be a mineral species. - [Distinguishing saussurite from jade by macroscopic means can be difficult -- e.g., both its typical hardness and specific gravity fall within the range of those of jade; thus, it is fortunate, and noteworthy, that saussurite is rarely found in pieces of desirable color that are large enough to be carved (etc.) so it has found little use as a jade substitute.].
    • Serpentine (in some cases dyed or otherwise treated). Several serpentine-rich rocks and mixtures of serpentine and other minerals, especially chlorite, have been called jade. (Interestingly, a coated nephrite carving is recorded by Wentzell (2004) to mimic serpentine.) So far as the serpentine rocks that have been called jade in the marketplace, most have some modifying (redeeming?) adjective --commonly based on their source area -- modifying the jade designation: Among these are Korean jade (see below), Marble Bar jade, New jade, Oceanic jade, Pilbara jade, Qilian jade, Styrian jade (see separate listing), Sushou (Souchow) jade (see below), Xiuyan jade and Xinyi jade. Marble Bar jade and Pilbara jade, by the by, are two designations given one and the same serpentine-chlorite rock that comes from the vicinity of Marble Bar, Western Australia. - [inferior hardness (H. 5); characteristic waxy luster not characteristic of jade (especially jadeite)].
      Four serpentine family members follow:
    • antigorite - Korean jade.
    • bowenite - this variety of serpentine from several localities has been used as a jade substitute. Examples are Milford Sound, New Zealand where it is commonly called New Zealand jade or, less commonly, tangiwai -- tangawaite or tangiwai is a Maori term meaning tears; Afghanistan, where it was originally called sang-i-yashm and only recently equated with bowenite; and China, where it has been given the names Sushou jade and Korean jade. In addition, bowenite from its type locality in Rhode Island has been referred to as Rhode Island jade.
    • verde antique (serpentine marble) - see SERPENTINE entry.
    • williamsite - massive variety of antigorite, commonly containing chromite (see Fig. C on SERPENTINE entry).
    • Serpentine-calcite rocks - selectively dyed and commonly coated with, for example, wax or paraffin - [Wax or paraffin can be detected by heating; both serpentine and calcite have inferior hardnesses; calcite effervesces with dilute HCl.].
    • Siberian blue nephrite (also called dianite) - a massive blue (diverse hues) quartz, tremolite, magnesio-arfvedsonite rock, the texture of which resembles nephrite jade from an unspecified location, in Siberia (Johnson et al., 2000).
    • Sillimanite (variety fibrolite) - [Distinguishing this material from jade can be difficult in hand specimen. Fortunately it is relatively rare in pieces large enough to be carved (etc.), and consequently has been so-used only rarely.].
    • Silver peak jade - misleading name sometimes given malachite - [inferior hardness (H. 3½ -4); effervesces with warm dilute HCl; appearance].
    • Smithsonite (apple-green variety also referred to as bonamite) - [inferior hardness, effervesces with warm dilute HCl].
    • Soapstone - see Talc.
    • South African jade - see Garnet.
    • Steatite - see Talc.
    • Styrian jade - rock consisting largely of an aluminous serpentine (sometimes incorrectly called pseudophite), plus pinite (name sometimes applied to massive fine grained mica, typically muscovite) and clinochlore (a chlorite). Much, if not all, of this rock that has been carved into ornaments and marketed as a jade substitute has come from east of Graz, Styria State, Austria - [inferior hardness].
    • Syenite (marketed as jadeolite) - a deep-green chromiferous syenite from Bhamo, Myanmar (formerly Burma). - [Appearance is sufficient to distinguish this multi-grained rock from jade.].
    • Talc (as soapstone or steatite) - e.g.,Fujian jade, Henan jade, Manchurian jade, Shanghai jade, and Souchaw (=Suzhou) jade. - [inferior hardness].
    • Transvaal jade - hydrogrossular from Bufflesfontein - [higher specific gravity].
    • Turkish jadeite - this material is described as "a hard purple rock from Turkey with a moderately high jadeite content." The "moderately high jadeite content" is, however, described as typically less than eight (a "typo" for eighty?) percent jadeite (Ward, 1999).
    • Verde antique - see Serpentine.
    • Verite (also called Rhodesian jade) - a greenish rock composed largely of the green mica fuchsite along with scattered grains of rutile and one or more clay minerals - [inferior hardness].
    • Vesuvianite jade - a massive compact vesuvianite also called californite and frequently marketed as either American jade or California jade. - [Although some of this material easily fractures in so-to-speak random directions, for the most part, if the resemblance is good, it is difficult to distinguish from jade. Consequently, optical mineralogical tests, such as index of refraction determinations, are requrired.]. To find further information, recall that vesuvianite is recorded as idocrase in some books. See VESUVIANITE entry.
    • ***Victoria stone - name sometimes given Iimori stone -- see Glass.
    • Volcanic ash - "green volcanic ash in silica" is recorded by Weldon (2007). I am not sure what this is because no description is given; perhaps it is glass.
    • ***Wax (as in candles) - some wax figures, especially those with shapes that mimic Chinese genre jade carvings, closely resemble jade - [inferior hardness; different "feel"].
    • White jade - actually a composite of quartz and albite with small amounts of nephrite from central Wyoming. - [Multi-mineral makeup suffices to make distinction.].
    • Williamsite - see Serpentine.
    • Yü - "The Chinese term Yü which is translated to the strict term Jade in English (i.e., Nephrite and Jadeite) is much more loose in the original Mandarin and encompasses not only any hard green/greenish stone that can be worked for lapidary purposes but also carnelian (Man Ao). ... Man Yü and sometimes Man Ao is a reference to a red form of Agate or Carnelian which is very popular in China" (Jeffrey de Fourestier, personal communication, 2004). - [depends on stone used; if agate or carnelian, see Chalcedony].
    • Zoisite - the variety thulite is said to have been substituted for pink jade - [see ZOISITE entry].
    • In addition, gemstone doublets or triplets have been made of such materials as quartz and glass along with jadeite, and in some cases dyed. Also, carvings (etc.) that are so-to-speak assemblages that consist of "thin, hollowed-out shells of natural-color green jadeite jade and filled with a transparent, colorless plastic" have been marketed (Kammerling and Fryer, 1995, p.266-267).

    [gemma traslucida molto preziosa che corrisponde a due specie mineralogiche distinte GIADEITE e NEFRITE ]
    Nome tradizionale e commerciale della gemma o meglio della roccia preminentemente composta di GIADEITE oppure di NEFRITE, che è l'unico altro minerale commerciabile col nome di GIADA . Può presentare moltissime colorazioni nei vari toni del verde al giallo al bruno e perfino tonalità blu / viola
    Fin almeno dall'inizio del III millennio A.C. la giada viene tesaurizzata in Cina come pietra reale , YU. Si pensava che la giada preservasse il corpo dopo la morte gran parte del corredo funebre degli Imperatori era fatto di GIADA gia 5 millenni fa. Per millenni la Giada fu simbolo di amore virtù e immortalità, ma anche uno staus symbol. Nell'America Centrale gli Olmechi, i Maya, e i Toltechi anche usavano la giada per manufatti rituali e pregiati nonchè per incidervi siggilli, sfortunatamente gli Aztechi istituirono una forte tassa sulla Giada così molti oggetti d'arte precedenti vennero riciclati. La storia della giada in europa non è altrettanto nota, sebbene sono state trovate asce e manufatti di giada nei siti preistorici; alla maggior parte della popolazione la Giada era sconosciuta fino al XVI secolo quando cominciò ad essere importata prima dalla cina e in seguito dall'america centrale . I Portoghesi che portarono per primi la GIADA in Europa dal loro stabilimento di Canton la chiamarono Piedra de Ilharga, o "pietra dei lombi", perche si pensava fosse una potente medicina per le malattie renali . Gli oggetti di giada portati dagli spagnoli dal nuovo mondo vennero chamati nello stesso modo in spagnolo "Piedra de Hijada" da qui si diffuse in Francia come "ejade" e quindi Giada, jade etc.
    La giada lavorata dai cinesi era in realtà quel minerale della famiglia degli anfiboli che oggi chiamiamo NEFRITE (interessante notare che questo termine deriva dal Greco Nephros che significa Rene). Nel XIX secolo si scoprì che il minerale che proveniva dal nuovo mondo non era lo stesso che proveniva dalla cina. Il minerale che proveniva dall'America era costituito da Pirosseno, e fu chiamato Giadeite per distinguerlo dalla Nefrite originale.
    I Cinesi anche conoscevano la Giadeite , alcuni viaggiatori avevano riportato in Cina questo minerale da viaggi in Birmania agli inizi del XIII secolo, ma i cinesi che chiamavano questa pietra straniera La Pietra del Martin Pescatore, con riferimento ai colori brillanti delle piùme di questo uccelletto acquatico, non la considerarono mai vera giada. Divenne popolare solo nel XVIII e XIX secolo quando ricominciarono i commerci con la Birmania.
    Attualmente è la Giada di GIADEITE che è considerata vera Giada, spuntando prezzi ben maggiori della NEFRITE, poiche mostra colori verdi più vividi e una Traslucenza più marcata della Giada di Nefrite. Attualmente La GIADEITE e prodotta in Birmania dove il suo commercio e strettamente controllato da una impresa statale e viane venduta attraverso aste annuali a cui possono partecipare i più importanti commerciati di Giada del mondo. Ma queste aste sono una vera roulette russa in quanto i massi di Giadeite vengono venduti con una piccola porzione esposta così il compratore non sa che cosa vi troverà dentro: se della preziosa giadeite verde o del materiale molto modesto con clorazioni biancastre o marroni. Il compratore deve basare tutto sull'Istinto e pagare centinaia di migliaia di dollari. La Giada più bella viene solitamente tagliata in Cabochon , ma si possono avere bracciali più o meno tubolari che sono molto popolari in asia, o anche varie forme in placchette o figurine varie. Alcuni collier realizzati in Giada durante il periodo dell'Art Decò hanno spuntato valutazioni di centinaia di migliaia di dollari in aste recenti. A causa della sua struttura relativamente tenera la GIADA ben si presta all'intaglio e alla scultura e alla creazione di differenti forme con cui vengono realizzati collane e bracciali. La giada viene venduta principalmente come pezzo di gioielleria più che a carato , e nella sua valutazione , subito dopo il colore si prendono in considerazione la traslucenza la struttura e il disegno, certi particolari disegni sono particolarmente valutate come il cosiddetto "Muschio innevato".
    Il Buddha di Smeraldo esposto al culto nel tempio buddista di Wat Phra Kaeo a Bangkok in Tailandia è realizzato in giadeite verde.
    La GIADA di GIADEITE e più apprezzata per il suo colore Verde vivido, ma può anche presentarsi con colorazioni Lavanda, rosa, giallo e bianco. Mentre la maggior parte della GIADEITE proviene dalla Birmania, piccole quantita si rinvengono in Guatemala, benchè siano state ritrovate degli utensili in Giadeite di etá preistorica in europa , non è ben chiaro dove questa venisse estratta , ma quasi certamente essa veniva trovata nella catena alpina.
    La NEFRITE si trova in colorazioni Verdi meno intense della Giadeite, ma anche in colorazioni bianche marroni o nere. Oggi proviene principalmente da Canada, Australia, Usa e Taiwan .
    Attualmente la maggior parte della GIADEITE viene trattata con cera alla fine dei processi di lavorazione e ciò viene considerata commercialmente un trattamente accettabile, tutti gli altri trattamenti sono considerati inaccettabili e quindi ne diminuiscono il valore. Alcune Giadeiti vengono colorate di verde o con altri colori queste giade colorate tendono a sbiadire col tempo. Altre giade vengono sottoposte a trattamenti di sbiancamento e quindi impregnate con resine polimeriche (B-jade). Pertanto al momento di acquistare delle gemme importanti di Giada si consiglia di farle analizzare per determinare gli eventuali trattamenti a cui siano state sottoposte.
    La Giadeite sintetica è stata prodotta per prima della General Electric e il perfezionamento del processo permette attualmente di produrre materiale di buona qualità, ma questi materiali rono rari da trovare nei normali canali commerciali essendo ancora ampiamente sperimentali. Di contro le imitazioni della giada sono moltissime fra queste ricordiamo dei vetri verdi ma anche gemme naturali come idrogrossularie, serpentini e molte altre.


    GIADEITE (en: jadeite)

    [InoSilicato - Monoclino -NaAlSi2O6 - Hm: 6,5-7 - Ps: 3,3-3,5 g/cm3;insolubile in acidi]
    JADE (jadeite) ( Fr- jade; Ger- Jadeit; Nor- jadeitt; Rus- ) JADE (jadeite), Na (Al,Fe)Si2O6. DESCRIPTION: Pyroxene jade consists wholly or largely of microcrystalline, typically blocklike grains of jadeite. The size and arrangement of the grains appears to account for the unusual toughness of this jade and also its relatively common grainy or dimpled appearance, which is evident when fractured surfaces are viewed with a handlens or simple microscope. Guatemalan jadeite, which is somewhat atypical, tends to be relatively coarse grained, commonly including grains large enough to be seen with the naked eye; in addition, some of it includes chromium-bearing minerals such as macroscopically discernible chromite. Some jadeitic jade -- e.g., that from the famous Myanmar (formerly Burma) localities -- contains noteworthy amounts of other minerals such as acmite, actinolite, albite, analcime, edenite, diopside, enstatite, kosmochlor, muscovite, natrolite, nepheline, prehnite, richterite, tremolite and wollastonite. Geologists, in particular, refer to these impure jades by special names -- e.g., those with noteworthy amounts of diopside and/or acmite, which are typically dark green or nearly black, are often termed chloromelanite. See THE JADES entry for colors and some of the other properties that pertain to both Nephrite and Jadeite jade. H. 6½ - 7 (typically slightly harder than nephrite) S.G. 3.28-3.40 Light transmission - subtransparent to opaque Luster - ranges from glassy to oily or porcelaneous Miscellany - many jade boulders have reddish, yellowish, orangy or brownish rinds.
      OTHER NAMES: Scores of names have been applied to jadeite jade. Jill Walker in the tome edited by Keverne (1992) lists "common trade names" (i.e., both adjectives and complete designations for jadeite jade) as follows:
    • Apple - yellowish green jade.
    • Black chicken - subtranslucent to opaque, unevenly dark gray to nearly black jadeite.
    • Chicken bone - opaque jade ranging from white to tan or gray in color.
    • Chloromelanite - subtranslucent to opaque, dark green to nearly black jade, typically containing noteworthy amounts of diopside and/or acmite; this designation is most frequently associated with jadeite jade from Meso America, but Fuquan (1979) also records "Jadeite (chloromelanite), an iron-bearing variety, is found in the province of Yunnan, Southwest China, and known as Yunnan jadeite.".
    • Emerald - see Imperial.
    • Fei-Tsui - name proposed by Ou Yang (2003-notes original reference) for "all precious stone jade composed of pyroxene group minerals."
    • Galactic Gold - marketplace name given to a black jadeite that contains bright metallic inclusions (possibly pyrite). --This designation is given some of the jadeite jade from Guatemala (Ward, 1999).
    • Hte long Sein (also called Tie, or Tian,long sheng) - a "fully saturated green" jade from the Pharkant mining district, northern Myanmar (formerly Burma).
    • Kimpi - name sometimes given to reddish or brownish jadeite.
    • Kingfisher (fei cui and some maw-sit-sit) - medium green jade.
    • Imperial - subtransparent to translucent, medium green to bluish green jade.
    • Moss-in-the-snow - translucent jade that is essentially white but has sporadic green streaks.
    • Russian Jadeite - Up until recently, gem-quality imperial jadeite was found only in Upper Burma. But starting in the early 1970's, jadeite was found at Itmurundy in Kazakhstan.
    • Siberian Jade - Negli anni 70, fine jadeite was found in the Polar Urals at Pusyerka, and in 1992, in Khakassia, about 100 km. outside of the capital of Abakan. The jade mines in Khakassia are situated near the banks of the Yenisey River, near Sayano-Shushenskaya, one of Russia's largest hydroelectric dams.
    • Yunnan - translucent to opaque, dark green jade.
    USES: See the many things listed under the USES subheading in THE JADES entry. In addition, some jadeite has been faceted for use in, for example, rings. And, some translucent, virtually colorless jadeite has been fashioned into cabochons that closely resemble moonstone. Also noteworthy: Today, much Guatemalan jade is fashioned into replicas of Olmec and Mayan carvings most of which are sold to tourists. In addition, special attention is directed to the book by Ou Yang (2003); in chapters six and nine, she lists and illustrates a few uses and outlines processes of production and systematically considers jadeite appraisal and grading factors (color, transparency, brightness, grainsize, cracking, volume, and cut). OCCURRENCES: Diverse -- e.g., in sequences of chiefly sedimentary rocks that have undergone relatively low-grade metamorphism and as dikes (lenses?) in serpentinites -- with less than a consensus among geologists so far as conclusions relating to their geneses; and as alluvial boulders derived from bedrock occurrences. Ou Yang (2003) lists the following occurrence designations: New Mine skinless stone ("unweathered ... in primary ... deposits"), Mountain stone (in mass wasting environments), Surface Water stone (angular pieces in rivulets), River stone (rounded stones in river beds), and Terrace stone (stones of whatever origin now occurring in terrace deposits). She also lists the following categories based on the common skins or crusts on these stones: Sandy skin (of various colors), water ("feels smooth") skin, and enamel skin. NOTEWORTHY LOCALITIES: Tawmaw plateau -- e.g., from Hpakan district, near the Uru River, about 65 miles from Mogaung, northern Myanmar (formerly Burma); and near Manzanal, Motagua Valley, Guatemala. Shigley et al. (2000) tabulate localities and pertinent references for localities from which jadeite was recovered during the 1990s. One recently discovered (rediscovered?!!) jadeite deposit seems especially noteworthy: Translucent blue and blue-green jadeite, which closely resembles that apparently used for millenia, by pre-Columbian Mesoamerican Olmecs, was so-to-speak unearthed in 1998. -- A major hurricane-promoted flooding of the Motagua River of Guatemala, and consequent landslides moved large "bus-size boulders of Olmec blue jade" to, for example, river beds, where they were washed clean; in addition, the movements exposed jadeite veins here and there in the bedrock (Broad, 2002). REMARKS: As already noted, some jade in the marketplace has been dyed, chemically bleached, coated with paraffin, wax or some resin and/or impregnated by a polymer (Fritsch et al., 1992). Other known treatments, used singly, together, or along with those just mentioned include vacuuming, the application of acid (commonly acetic acid) or a bleach to remove extraneous stains or other coatings, and heating to improve colors. Remarkably -- in my opinion, ridicuously -- some of the dyeing has involved differential application of the dyes purportedly to make the jade take a "more natural appearance." -- Wow! In general, jadeite jade, unlike some nephrite jade, does not become dull with the passage of time. It seems a bit ironic that the designation China jade is sometimes used in an almost generic way to refer to jadeite jade even though most jade pieces from China are nephrite jade. A jadeite boulder, reported to be the largest ever found, is on display in front of the Myanmar Gems Enterprise headquarters at Yangon, Myanmar (Koivula, Kammerling and Fritsch, 1992, p. 132). Apparently recovered from the Khy-Siu mine in the Mogaung area of Myanmar (formerly Burma) in July of 1982, the boulder has a circumference of 8.75 meters (~29 feet) and has been calculated to weigh about 33 metric tons (36 tons). SIMULANTS: See those given in THE JADES introductory entry. In addition, it seems noteworthy that some items fashioned from nephrite jade have been marketed as jadeite. Jadeite-resin doublets etc. - Such assembled stones, along with acid-treated and both resin-filled and resin-impregnated jadeite are well described by Ou Yang (2003, Chapter eight). ***Synthetic jade - "General Electric (GE) Gem Technology has developed a proprietary process for manufacturing synthetic jadeite . . . The samples [supplied the GIA Gem Trade Laboratory] ranged in color and quality ... but the finest green material rivaled 'Imperial' jade . . . [this . synthesis is said to be] achieved in a high pressure environment . . . [and] The gemological properties of the small number of samples we have tested to date overlap those of natural jadeite." (Moses, in Moses et al., 2002). REFERENCE: Hargett, 1990; Ou Yang, 2003.
    Una delle due specie mineralogiche che può essere venduta col nome di GIADA. Mineralogicamente la GIADEITE e un pirosseno che si presenta in ammassi compatti di colori generalmente fra il verde e il bianco, raramente ha una colorazione verde smeraldo nella mitica variatà estemamente Pregiata detta GIADA IMPERIALE.Ma buona paere della Giada usata per millenni dai cinesi era soprattutto composta da NEFRITE UN varietá dell'Anfibolo Actinolite.


    GIAIETTO (o GAGATE) (en: Jet)


    [ Carbon fossile : Lignite, Antracite / cfr: Carbone] JET ( Fr: jaïet, jais; De: Gagat,Pechkohle; Nrw:: gagat) Il giaietto o gagate è un mineraloide , una varietà di lignite, durezza 3-4 nella scala di Mohs, è quindi abbastanza fragile, di color nero brillante. Probabilmente devirato da tronchi d'albero fossilizzati risalenti alle epoche giurassiche e crataciche. Viene ampiamente usato in bigiotteria gioiellerie ed oggettistica molto usata come pietra ornamentale per oggetti funebri, o anche per ricavarne perle nere.
    Atraverso procedimenti di pulitura e lucidatura acquista una slpendida lucentezza che ha una notevole durabilità. Le auliyà migliori sebrano quelle che provengono dalla Asturia (Villaviciosa), dall' Inghilterra (Whitby), proviene la miglior varietà della cosiddetta "azabache", notevoli le varietà provenienti dalla Siberia.
    Il termine italiano "giaietto", deriva dal latino "Lapis Gagates", cioè pietra del Gagi, dal nome di un fiume, o addirittura di una reguione dell'Anatolia . Era detta anche Ambra Nera, interpretando male la sua origine, infatti non deriva da resine vegetali fossili ma da processi di fossilizzazione del legno , un carbone a tutti gli effetti ma più compatto e quindi più duro, che in qualche modo può richimare l'ambra.
    In italiano la parola giaietto per lo più indica una certa tonalità di nero, il "nero giaietto" in gioielleria vie ampiamente usato il termine inglese Jet o altri ttermini cge lo indicano.
    Come tutti i prodotti naturali il Giaietto deve nesessariamente avere una disponibilità limitata pertanto è stato variamente imitato. DESCRIPTION: Jet is a compact black variety of lignite (lignite is sometimes referred to as brown coal because it has a brown streak -- i.e., powdered lignite is brown). Although jet is usually characterized, quite properly, as dense and homogeneous, much of it exhibits a woody structure, which manifests its derivation from conifers. Color - commonly characterized as jet-, pitch- or velvet black -- i.e., intense black H. 2-4 S.G. 1.16-1.40 Light transmission - opaque Luster - velvetlike; polished, brilliant Breakage - conchoidal fracture Miscellany - tends to feel warm; becomes electrically charged when rubbed with cloth and thus will pick up such things as small bits of paper; flammable, giving an odor like that of burning coal. OTHER NAMES:
    • Agstein - a name formerly used for jet.
    • American jet - jets from Colorado (also called Colorado jet) and Utah (Utah jet). The latter includes inferior quality jet from Wayne County, Utah.
    • Azabache - Mexican jet.
    • Bastard jet - a soft jet; one source mentioned in the literature is Canada, not otherwise specified; certainly several other countries have jet of equally poor quality.
    • Black amber - name given in the Middle Ages, apparently because of its becoming electircally charged like amber was then known to react (King, 1865); this designation is also applied, albeit rarely, as a trade name for "polished velvet black coal," which, if marketed as jet, is a simulant - [see COAL entry]. .
    • Canadian jet - jet from Pictou, Nova Scotia, Canada.
    • German jet - a generally inferior jet from Saxony and the Swabian Alps, where it is also called Württemberg jet.
    • Montana jet - a misleading misnomer given some black obsidian from the Yellowstone National Park area, Wyoming.
    • Russian jet - jet from the vicinity of Irkutsk, Siberia.
    • Sapropelic coal - see under SIMULANTS.
    • Scorpion stone - name sometimes applied to jet, but also to coral.
    • Whitby jet - jet from coal mines near Whitby, Yorkshire, England. Many connoisseurs consider this jet to be the best ever found and fashioned for use in, for example, jewelry.
    • "Witches amber" - name given to "necklaces of alternating Amber and Jet . . . [worn by] Wiccan High Priesteses (White Witches)" -- (www.luckygemstones.com/jet-jewelry-black mourning-gem.htm)
    USES: For the most part in mourning jewelry -- e.g., brooches, pendants and beads, commonly faceted; for statuettes, carvings and souvenirs; as the base material for pietra dura; and rarely for such things as carved plaques and rather small vessels of several genre. An eight-foot long necklace ("rope") of polished jet is recorded by Crowningshield (1963). OCCURRENCES: Within carbon-rich beds in predominantly shale strata. So far as the origin, Stutzer (1940, p.270) notes that "during the process of coal formation, wood fragments frequently become impregnated with dissolved products of decomposition ... [and a material is formed that is] dense and pitchlike. This process has sometimes but not very correctly been called 'gagatization,' because gagate, or jet, originates in a similar way by saturation of wood with organic substances, primarily hydrocarbons." NOTEWORTHY LOCALITIES: Near the coast in the vicinity of Whitby, Yorkshire, England; Languedoc, France; Oviedo (formerly Asturias), Oviedo Province, Spain; El Paso County, Colorado. REMARKS: The term jet is usually indicated to be from Middle English after Anglo-Norman geet, from the Latin gagates, from Greek gagates, for Gagas, a town of Lycia (an ancient region/Roman province on the Aegean Sea, southwest of Asia Minor). This is particularly interesting (confusing?) when one considers the currently prevalent status accorded gagate -- see under SIMULANTS subheading. Jet is flamable, so one should avoid heating it. Also, anything made from jet should not be put in contact with acids because such contact tends to cause its surfaces to lose their luster. Jet pieces apparently shaped by flint tools have been found with other paleolithic materials within caves in Canton Schaffhausen, Switzerland and in Belgium. A photograph of a necklace with carved jet beads – “made by Magdalenian craftsmen, ... [ca.]13,000 B.C.” – found near Petersfels, which is northeast of the Bodensee in southwestern Germany, is shown in Dubin (1987). Artifacts made from Whitby jet have been recorded as dating to at least the 2nd Century B.C -- the existence of this material, however, is doubted by some professional archaeologists. During the 1500s, many Rosary beads were made from jet, which was frequently dubbed "black Amber." Also, jet beads were among the artifacts found at the site of Raleigh Gilbert's house at Fort St. George, which was the 1607-08 English Popham Colony at the tip of Sabino Head, near the mouth of the Kennebec River, Maine (www.pophamcolony.org). It was not, however, until Queen Victoria mourned Albert and wore jet jewelry with her black attire, that jet gained real popularity; thereafter, it was considered widely -- especially in Great Britain -- to be the appropriate jewelry to wear at funerals. Along this line, at least in my mind, a remarkable (sub)parallel use is recorded on the following web site: www.luckygemstones.com/jet-jewelry-black mourning-gem.htm:. "The Pueblo Indians were known for burying Jet with their dead. A famous, exceptionally beautiful and well-made frog carved from Jet and inlaid with Turquoise eyes, was discovered in the Pueblo Bonito in 1896 by Mr. Pepper. It is believed these Indians thought Jet would protect them in the after-life." Also noteworthy, I think, are the following selected descriptive lines in the English translation (King, 1865, p.388), of a poem said to have been written in the 4th Century A.D. and attributed to Orpheus: " ... when Jet in rising clouds consumes, The nose provoking with its pungent fumes. Black as a coal, but yet of lustrous shine, It blases up like torch of driest pine;..." The fact that the chain links, as well as the pendant, of the necklace shown as Figure A are jet was of special interest to me, whose experience in small scale carving has been limited to fashioning diverse things from peach pits. In answer to my queries, David Hartley (personal communication, 2003) notes "To learn to carve jet involved a 5/7 year apprenticeship to a master carver. [and] links like these were usually carved in two halves and joined by very fine pins....no glue." In addition, he added "the only Jet that could be carved and polished to this degree was from Whitby and is instantly recognised as such by an experienced dealer....[-- e.g.,] jet from Spain often split and with time fractured further [whereas] Whitby Jet never fractures in this way, and is of a uniform color, without brown marks or stains." If one looks at catalogs from museums and specialty houses, it would be logical to think that jet has been gaining popularity recently-- faux jet necklaces and earrings appear to be advertised with increasing frequency. SIMULANTS: The designation jet is usually indicated to be from Middle English after Anglo-Norman geet, from the Latin gagates, from Greek gagates, after Gagas, a town of Lycia, which is (an ancient region/Roman province on the Aegean Sea, southwest of Asia Minor). - [see OCCURRENCES.]. Anthracite - a possible but, so far as I have been able to determine, never used substitute for jet; it does, however, have gemrock uses similar to those of jet - [See COAL entry.]. Asphaltic pyrobitumens - To date, I have not seen asphaltic pyrobitumens and related materials recorded as having been used as a jet substitute or even being used in jewelry or fashioned pieces. This indicated neglect seems odd because some of these substances have characteristics that would appear to make them quite suitable for such use. Examples of these substances, listed alphabetically, are albertite, anthraxolite, asphaltite, gilsonite, glance pitch, grahamite, impsonite, libolite, stellarite, unitaite (=unitahite), and wurtzilite. I have seen some of these materials labeled as coming from localities in the Uinta Basin, Utah and Montgomery County, Virginia; Alberta and Nova Scotia, Canada; and Angola. Each is considered as possibly derived by so-to-speak metamorphism of petroleum. Augite - see Black minerals. ***Bakelite - a trademark name given to a number of synthetic resins and plastics, some black ones of which have been used as substitutes for jet - [Appearance usually suffices in that most, if not all, so-constituted items are molded rather than carved; also, these items commonly bear a trademark or patent notice.]. Black amber - see under OTHER NAMES subheading. Black "coral" - marketplace name given a bryozoan from Hawaii. - [effervesces in dilute HCl]. Black minerals - e.g., black augite, garnet (melanite), sphalerite, spinel (hercynite), and tourmaline (schorl). - [Each is markedly harder than jet and feels cold as compared to jet (see Johnson, McClure & DeGhion, 1996).]. Cannel coal (candle coal in some records) - homogenous, dull, compact coal of bituminous grade. - [Has black streak; does not take a good polish, tends to be more brittle; can be seen under a simple microscope to consist largely of spores - see COAL entry.] Chalcedony dyed black. - [superior hardness (H. ~7)]. ***Crepe stone - black glass with a dull crepelike appearance, used especially in mourning jewelry. - [See Glass.]. Dolostone - A "quartzite and dolomite" rock, which on the basis of the description given seems likely to be a quartz-bearing dolostone, has been recorded as having been fashioned into a gemstone (Hargett, 1991). As illustrated, it is black and would apparently be a good substitute for such gemrocks as onyx or jet. -- Although Hargett does not indicate that the rock was dyed, it would seem very likely it was because black dolostones are rare, if indeed they exist. - [effervesces, albeit with a slow simmering, when attacked with dilute HCl]. ***Ebonite (also called vulcanite) - black vulcanized – i.e., hardened – rubber, used in some mourning jewelry. - [Facets on ebonite used for beads (etc.) are formed by molding of the precursor fluid so the sharp edges characteristic of those generally produced by cutting and polishing jet are lacking; also, when touched with a hot needle, ebonite will emit the odor of burning rubber; and, some vulcanite tends to fade to a tan or olive-brown color when left in the sun for relatively long periods of time.]. ***French jet (a glass). - according to David Hartley (personal communication, 2003) "The most successful imitation [of Whitby Jet] was known as 'French Jet' and while it was able to imitate the lustre of polished Whitby Jet, it was cold and heavy in comparison to the real thing." - [The facets on this glass used for beads (etc.) are formed by molding of the precursor fluid and consequently lack the sharp edges common to those made by cutting and polishing jet; also, glass is not affected by a hot needle and is heavier than jet.]. Gagate (gagatite) - a coal-like rock that resembles jet. Unfortunately, the literature about jet and gagate is replete with ambiguities: Some writers have used the terms interchangeably. And, to add to the confusion -- especially for those of us who are interested in the etymology of words -- see first sentence under the REMARKS subheading and also the statement under OCCURRENCES. ***Glass - manufactured black glass, sometimes designated by such terms as faux jet and glass jet, is frequently used in jewelry. - [glass is harder (H. ~5 ½) than jet; feels cold; and, as already mentioned, most "faceted" pieces have actually been molded, which is obvious upon close examination.]. ***Gutta-percha - some of the mourning pieces of Victorian England were fashioned from this material, which may be described as a rubberlike substance that is derived from the latex of any of several tropical trees of the Palaquium and Payena genera. - [general appearance, "feel," and distinctive ordor given when touched with, for example, a hot needle]. Hercynite (black spinel) - see Black minerals. I have a faceted hercynite from a Virginia locality that closely resembles polished jet. - [superior hardness]. Horn (stained black) - [lower luster than that of jet; gray streak; when touched with a hot point, emits an odor like that of burning hair]. Irish Bog Oak - “was apparently never meant to imitate, but can be confused with jet. It has a distinct visible wood structure, is dark brown in colour and is generally carved in Irish themes such as harps, shamrocks and castles.” (www.antiquejewelryonline.com) Kimmeridge Shale - black bituminous shale from the Isle of Purbeck area of southern Dorsetshire, England. Although it appears that this shale has not been surreptitiously substituted for jet, some artifacts made from it resemble jet and have been so-designated in some collections. - [dull until smoothed and polished; texture]. Melanite (black andradite garnet) - see Black minerals. Montana jet - obsidian from Yellowstone National Park; see next listing. Obsidian - Black obsidian has been used in mourning jewelry. - [superior hardness]. Onyx (black portion) - black chalcedony. - [superior hardness]. ***Paris jet - a name sometimes given “French jet” (q.v.). ***Plastics, Resins (e.g., epoxy) - [Appearance usually suffices.]. ***Porcelain - black “jet porcelain” is sometimes fashioned into, for example, cabochons. - [superior hardness] Sapropelic coal (jet-sapropelite) - a "jet" in some people's minds, including mine, but not according to the widely accepted, restrictive definition that specifies a wood precursor. Sapropelic coal "jet," which has no relict woody structures, is thought to have had algae as its precursor. In Russia -- where it occurs near, for example, Irkutsk, Siberia -- it has been fashioned into such things as long Turkish pipes, spoons, bowls, diverse carvings, and pieces of jewelry including hololith rings since at least the late 1800s (see, for example, Glushnev, 1995). - [exhibits no traces of woody structures; typically gives a light brown or yellowish streak]. Schorl (black tourmaline - also called jet stone) - see Black minerals. Sphalerite - see Black minerals. ***Vauxhall glass – a name sometimes given “French jet” (q.v.). ***Vulcanite - see Ebonite. Wood - examples are ebony and the so-to-speak partially fossilized bog oak of Ireland. - [lack of conchoidal fracture; without surficial coatings lower luster].

    Gillespite in sanbornite matrix

    spheres and eggs have been fashioned from this rock that consists of bright red streaks (veinlets?) of gillespite in an off-white sanbornite matrix from the La Madrilena mine, Baja California, Mexico.



    GIRASOLE


    Nome antico di una gemma di difficile identificazione, ma dalla descrizione si può intuire che è una pietra che presentava un qualche fenomeno di adularescenza o simile al gatteggiamento : Pietra di media diafaneità, con un riflesso rossetto che si muove come un'asteria al suo interno. E' di color Latteo con una sfumatura turchina (forse un'adularia).


    GOOSECREEKITE

    [rara gemma da collezione]
    • Colore:
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    • Origine: .



    GORGEYITE

    [rara gemma da collezione]
    • Colore:
    • Durezza Mohs:
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    • Origine: .



    GOSHENITE (var. BERILLO)

    [Berillo Incoloro]

    GNEISS

    [Roccia Metamorfica originariamente Mgmatica // Cfr Migmatite ]
    A. Gneiss paperweight (width - 6.3 cm) made from Randesund banded gneiss from the area east of Kristiansand, southern Norway. R.V. Dietrich collection. (© photo by Dick Dietrich) B. Gneiss paperweight (width -10 cm) made of faulted gneiss, that consists of alternating black amphibole-rich and white quartz-rich bands; piece is a sliced and polished cobble found in the drift in Isabella County, Michigan. R.V. Dietrich collection. (© photo by Dick Dietrich) C. Granitic gneiss cobble (greatest dimension - 9.5 cm), given to RVD because it exhibits a "D for Dick", from beach at Whitefish Point, Chippewa County, Michigan. R.V. Dietrich collection. (© photo by Dick Dietrich) DESCRIPTION: Gneiss (pronounced nice) has been defined differently by different geologists. In this document, the following definition pertains: Gneiss is a roughly foliated or banded metamorphic rock that consists largely of granular minerals such as quartz. Colors - commonly black and white or black and salmon pink to nearly brick red; less commonly predominantly diverse green hues, off-white, or dark lilac H. (effective hardness -- usually due to quartz content) 7 S.G. 2.5 - 2.7 Light transmission - overall opaque but thin slices or, for example chips may have parts that are translucent or even subtransparent Luster - overall dull, especially on weathered surfaces, but on freshly broken surfaces individual constituent mineral grains range from dull, through pearly, to vitreous Breakage - irregular Miscellany - predominance of macroscopically distinguishable granular minerals and rough foliation or banded appearance are distinctive. OTHER NAMES: Most geologists refer to gneisses with either two or three names. Those with two names are named in accordance with the scheme whereby ... Gneiss has the ellipsis replaced a geographic name. The geographic term is given in accordance with the standards used to name stratigraphic units (see Appendix B, Glossary). The well-known Baltimore Gneiss of the Piedmont-Blue Ridge province of the mid-Atlantic United States is an example. Gneisses with three names have an additional so-to-speak middle name; that a dditional part of the name is descriptive and may relate to such things as the presence of augen, a banded appearance, the overall lithological identity of the rock, the presence of a certain mineral, etc., etc. Examples of these tripartite designations are, respectively, the Little River augen gneiss, the Randesund banded gneiss, the Herma granitic gneiss, and the Lynchburg garnetiferous gneiss, and, so far as the "etc., etc.", other aspects and examples of the resultant names seem too numerous, and relatively unecessary, to list here. It also is noteworthy, however, that in the laboratory and in the marketplace, the geographic locality of the bedrock occurrence of a given specimen of gneiss or of the gneiss used to fashion a given item may not be known. These gneisses are usually referred to by only their descriptive (middle) name plus the word gneiss -- e.g., faulted gneiss and granitic gneiss (see Figures B & C). USES: Paper weights, bookends, statuettes, bowls, etc. OCCURRENCES: Relatively common in metamorphic rock sequences, especially those including rocks with overall granitic compositions. However, the precursor rocks of gneisses may have been sedimentary rocks, volcanic rocks, igneous rocks, migmatites or virtually any combination of those rocks. NOTEWORTHY LOCALITIES: In metamorphic terranes here and there throughout the world. REMARKS: This rock name comes from the German Gneis, which apparently came about as an alteration of Middle High German gneist, which in turn appears to have been derived from the Old High German word gneisto; gneist meant spark so it seems that its application to this rock may have arisen as a reference to the "sparkling" appearance that many gneisses exhibit. As a so-to-speak connoisseur of gneisses (e.g., Dietrich, 1960), a little known fact that has long stuck in my mind since I heard it several decades ago is that Henry A. Ward, founder of Ward's Natural Science Establishment, for many years the major supplier of mineral and rock specimens to schools inter alios, is said to have collected the gneiss pebble, which is preserved at the company headquarters in Rochester, New York, when he was only three years old. Two gneisses I have seen fashioned into particularly attractive functional ornaments -- i.e., paper weights and bookends -- crop out here and there in the Blue Ridge Province of southwestern Virginia, western North Carolina and eastern Tennessee. One is a handsome overall light gray augen gneiss the feldspar "eyes" of which are all about the same size and distributed evenly throughout the rock; the other is the gneiss with the blue quartz "eyes" that is noted in Appendix A. In a campaign launched by the Norwegian Broadcasting Corporation (NRK), whereby people were invited to vote (by telephone) for their favorite mountain, Stetind Mountain, Nord, obtained the largest number of votes (Nordgulen, 2002 & Halfdan Carstens, editor of GEO, personal communication, 2002). A fine photograph of this mountain, which consists largely of a granitic gneiss, is shown in Nordgulen's article. As a consequence of the voting, this salient -- which is between Tysfjord and Æfjord (shown as Efjorden on current geographical maps) and about 30 miles (50 km) south of Narvik -- was assigned the title "Norges nasjonalfjell" (Norway's national mountain). One result, I suspect, will be that many tourists will make a point of going to see this striking landmark, and, in turn, it seems likely that entrepreneurs will fashion and market diverse ornamental pieces made from this gneiss. In literature, several rocks used for such things as beads have been designated gneiss although petrographers would give them other names; one example is amphibolite - see AMPHIBOLITE entry. SIMULANTS: ***Glass - both Venetian and African glass made to resemble gneiss comprise a bead necklace illustrated by Liu (1995, p.10-11) - [Resemblance is only rough so appearance suffices.]. REFERENCES: No general reference. Dietrich, 1960.

    GOLD Quarzite (Quarzite Aurifera)

    [(also called butter gold and jewelry rock)]
    Gold-bearing vein quartz "free gold dispersed in tiny crystalline aggregates and in small veinlets" in quartz veins, from Ouray and San Miguel counties is described as "one of Colorado's well-known lapidary materials ... used in jewelry."
    Murphy and Modreski (2002)

    GOODLETITE ( Cfr: Ruby Fuchsite)

    [ Nuova roccia Metamorfica Rubinifera // Cfr Fuchsite] Questa nuova rocca metamrfica proveniente dalla Nuova Zelanda ed è essensialmnete coposta da: Fuchsite, Margarite (e Muscoivite), Rubino , più o meno zaffiri e tormaline questa coloratissma roccia usata come gemma deve il suo nome Mr. William Goodlet. Può anche contenere Muscovite e zaffiro quantità variabili di Cromite e altri minerali del gruppe della Tormalina ancor non ben identificato. Il giacimento principale è a Back Creek, Rimu, nell'Isola meridionale della Nuova Zelanda.
    A. Goodletite cabochon (27.94 ct) fashioned from rock from South Island, New Zealand. H. & H. Bracewell collection. (© photo by Grahame Brown) B. Goodletite from the South Island of New Zealand as viewed with a hand lens - representative circular section was selected from Dr. Brown's original rectangular photo to direct attention to the handlens aspect of the illustration. H. & H. Bracewell collection. (© photo by Grahame Brown) C. Goodletite cabochon (vertical dimension - 2.0 cm) made from rough from near Hokitika, South Island, New Zealand. This cabochon, actually a doublet with a quartz dome, consists largely of blue sapphire, red ruby and green chromian mica plus minor tourmaline. New Zealand Ruby Rock Ltd. (© photo by Gerry Commandeur) DESCRIPTION: This gemrock, which I have not seen, has been described differently in different publications. O'Donoghue (1997) describes what he calls "Two types of goodletite" -- 1."green only ... [that] could pass as 'jade' to the unwary" and 2.something roughly similar to that described by Brown and Blackwell (1996), which Brown (personal communication, 1998) has clarified simplified as consisting of "anhedral grains of ruby and sapphire in a matrix of green chrome-rich mica and green tourmaline." Mitchell (1985) gives yet another definition as his #1: "Green-pyroxene or green-amphibole rock containing ruby corundum." Grapes and Palmer (1996) note that the mica content is chromian muscovite and margarite, typically with larger percentages of the muscovite and that some of the rocks contain noteworthy amounts of chromian chlorite, Zn-Mn chromite and Mn-Ti magnetite. To further complicate application of this name, Shipley (1951) notes that it is "A name for Burmese marble forming matrix of rubies." The following, slightly modified, is based largely on Brown and Blackwell's data and description, which seems well founded and relatively complete on the basis of what I have seen in photographs of the material. Colors - the green appears to largely, if not wholly, due to green mica (i.e., chrome muscovite) and/or green tourmaline; the red is red corundum(~ruby) and/or pink tourmaline; the blue is blue corundum(sapphire) and/or bluish tourmaline; the pinkish gray is corundum. Properties of these typically present macroscopically visible constituents follow: H. effective hardness, is due to presence of the corundums -- H. 9; other values are muscovite -- H. 2½ - 3; margarite --H. 3½ - 4½; and tourmaline -- H. 7. S.G. 3.3 - 3.8, which ranges with the percentages of the different minerals present in any given piece; specific gravity of the chief minerals are: corundum -- 4.0 - 4.1; margarite ~3.1; micas ~ 2.8; tourmaline ~ 3.25. Light transmission - overall translucent to subtranslucent Luster - overall subvitreous Miscellany - Each individual specimen, piece of rough and article fashioned from this rock is likely to look rather different from others. The differences, on the basis of photographs I have seen (and I should add quite what one should expect), are more marked than for nearly all other coarse grained gemrocks. So far as the appearances of the chief constituents, the following seem noteworthy: Corundum breaks perpendicular to the long dimension of prismatic grains to give virtually perfect to roughly hexagonal flat surfaces that have the appearance of fair to good cleavage -- actually, these surfaces represent a property called parting. Tourmaline grains that occur as crystals commonly appear to be striated parallel to their lengths and have cross-sections that resemble spherical triangles. The fact that fuchsite and other green micas exhibit perfect cleavage into elastic sheets is of little use so far as macroscopic examination because the mica in these rocks typically comprises fine grained masses in which the cleavage is not discernible. OTHER NAMES: Ruby rock - locally applied name in New Zealand; sometimes also used in marketplace. "New Zealand ruby rock" - extension of "ruby rock" that currently is applied rather widely in the marketplace. Treasure stone - locally applied name. USES: Composite gemstones (doublets and triplets), usually relatively large so all (or most) of the contituent minerals are present (see Figure C) -- however, individual minerals have been highlighted in stones, most of which are cabochons or free forms, used in rings and smaller pieces; also miscellaneous ornaments. OCCURRENCES: This rock has not been found in place -- i.e., as bedrock. It has been found only as cobbles and boulders in glacial moraine debris and in rivers of New Zealand's Southern Alps. On the basis of extensive petrographic and chemical studies Grapes and Palmer (1996) conclude that the rock was formed by "extrene metasomatism of quartzofeldspathic schist enclaves in serpentinite" of the ultrabasic complex east of where the boulders were found. Indeed, at least one boulder had serpentinite spatially associated with this rock. NOTEWORTHY LOCALITIES: Six localities east and south of Hokitika, Westland, South Island, New Zealand. REMARKS: This gemrock was named after William Goodlett, who isisaid to have taken a sample of the rock for identification and examination to Otago University, Dunedin, New Zealand. Despite O'Donoghue's previously cited statement implying that goodletite resembles jade, he adds his opinion to the effect that the color resembles "the 'Bonamite' variety of smithsonite more than either of the jade minerals." From the several photographs and other descriptions of these I have seen, this statement leaves me "at loss." According to Mitchell (1985) the name goodletite has also been applied to a rock from Myanmar (formerly Burma) that consists of rubies and their surrounding marble matrix. I have been unable to find such application of the name. In any case, this use should be abandoned. In fact, one has to wonder if it might be prudent to abandon the name goodletite -- which, at best, is an informal name for the rock(s?) described in this entry -- so far as applying it to any rock. But, consider the following: 1. this New Zealand rock does not seem to fit into any petrographic pigeon-hole; 2.although its origin has been hypothesized (see under OCCURRENCE subheading), its geologic occurrence (other than as loose boulders) is not known; [and] 3.without such fit or occurrence information, any at all logical name -- e.g., listing its constituent minerals -- would be far too cumbersome for the marketplace. Thus it appears that at least for the time being Goodletite is the name to use for these rocks (but NOT for the just described ruby-bearing marble from Myanmar), eh!?! SIMULANTS: None that I have seen or seen described. REFERENCE: Brown and Blackwell, 1996; Grapes and Palmer, 1996; O'Donoghue, 1997


    GOSHENITE (Berillo)

    [BERILLO INCOLORO]
    Varietá incolora del BERILLO, è anche relativamente raro, deve il suo nome alla località ove fu riconosciuta per la prima volta Goshen nel Massachusetts. Già i Greci usavano berilli incolori o pallidi come lenti.

    GRANATO (en: Garnet )

    [TectoSilicati - cubici ]
    • Colore:
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    • Indice di rifrazione:
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    • Chimica: -X3Y2(SiO4)3 ; X= Ca,Fe,Mg,Mn Y= Al,Fe,Cr
    • Cristallo:
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    • Polimorfi :
    • Origine:
    • Varietá :

    Dal punto di vista mineralogico i grananti costituiscono due serie di termini di soluzioni solide chiamati: PIRALSPITE e UGRANDITE cioe piropo-almandino-spessartina e uvarovite-grossularia-andradite , che sono ampiamente miscibili tra di loro ma gli scambi fra le due serie sono molto limitati.
    Quindi si deve parlare di un gruppo mineralogico da cui si hanno gemme di vario colore: Rosso scuro, arancio mandarino, verde lime , rosa bluastro il granato può avere tutti questi colori e anche di più, anche se il termine eminentemente gemmifero è la Grossularia ma anche gli altri termini a volta danno bei cristalli gemmiferi come L'Andradite che da il demandoide e la spessartina e l'uvarovite che danno bei cristalli da taglio.
    ALMANDINO
    ANDRADITE - Varietá: DEMANTOIDE
    GROSSULARIA - Varietá: HESSONITE , TSAVORITE , CROMOGROSSULARIA
    PYROPO: varietá RODOLITE
    SPESSARTINE: Varietá GRANATO MANDARINO
    UVAROVITE
    Ci sono granati che mutano colore con luce differente, grananti verdi traslucidi che sembrano giada e granati stellati. Il nome probabilmente deriva dal melograno (pomegranate). Molto famosa nel XIX secolo era la gioielleria cecoslovaccha e bohema dei granati e ancora oggi famosa, anche se oggi i granati vengono estratti in tutto il mondo . Le varietá esistenti sono distinguibili in base alla loro mineralogia o alla variazione di colore e raramente per l'origine: RHODOLITE, MALAYA, DEMANTOIDE, PIROPO, GROSSULARIA, HESSONITE, SPESSARTITE, TSAVORITE, ALMANDINO, GRANATO MANDARINO e GRANATO CANNELLA o CINNAMOMO.
    I GRANATI sono gemme abbastanza dure e durevoli ideali per la gioielleria, tranne il Demantoide che è meno duro e richiede più attenzione, ma è altrettanto vero che è rarissimo e difficilmente reperibile sul mercato. Le varietá rosse vengono imitate praticamente solo da un corindone sintetico rosso scuro che può essere scambiato per PIROPO o ALMANDINO. Per distinguere fra di loro le qualità rosse o arancio o dalle numerose pietre naturali che sono somiglianti è necessario analizzare in laboratorio le caratteristiche fisiche delle gemme: quindi bisogna ricorrere a rifrattometri, bilance per misurare la densità, il polariscopio e il microscopio(almeno una buona lente 10X) e a volte è necessario perfino lo spettroscopio.
    La RHODOLITE varia dal rosa al rosso violaceo ed è prodotto in Africa, India e Sri Lanka.
    La TSAVORITE varia da un giallo verde brillante fino a un verde erba dall' Africa Orientale.
    Il leggendario DEMANTOIDE combina un colore verde brillante con una brillantezza abbagliante che conquistò la corte degli Zar , che lo usarono con molta prodigalità. In passato il Demantoide si trovava solo di piccole dimensioni ed era estremamente raro , nel 1998 è stato scoperto un nuovo giacimento in Namibia , ma la gemma e ancora oggi rara .
    Il MALAYA, un'altra varietá mista molto popolare, varia da una colorazione arancione fino a giallo oro, si estrae in Kenia e Tanzania.
    Il PIROPO, che e un termine mineralogico, mostra il tipico rosso molto saturato dei granati, dei piccoli granati molto belli del PIROPO trovati in arizona sono detti "granati del formicaio" perche le formiche li portavano in superficie mentre scavavano il loro formicaio.
    Il Granato MANDARINO e una SPESSARTITE arancione brillante che sta riscuotendo molto successo fra i collezionisti da quando e stato recentemente scoperto un nuovo giacimento in Namibia
    Le HESSONITI e le SPESSARTITI principalmente si trovano in colorazioni dorate arancioni e marroni e talvolta vengono chiamati GRANATI CINNAMOMO o GRANATI CANNELLA.
    La GROSSULARIA, la varietá di granato che da la TSAVORITE, si trova anche in colorazioni rosa pallido, verdi e gialle.

    GRANATO KASHGAR (en: Kashgar Garnet)


    Nuova granato massivo scoperta nella Cina settentrionale, roccia di granato da traslucido ad opaco che deve il nome alla famosa città di Kashgar, la nota città-oasi lungo la via della seta che collegava l'estremo oriente col vicino oriente. Colori rosso e verde terra che richiamano la struttura di certi marmi, la pietra prende una bella lucentezza, che ne aumenta il fascino, ottimo material eper gioie durevoli .

    GRANATO MANDARINO (en: Mandarin Garnet)


    Varietá gemmifera della già rara SPESSARTINA di un bel colore Arancio Brillante scoperta in Namibia nel 1991, vicino al confine Angolano, dove per la prima volta si sono potute avere delle pietre di grande qualità in quantità economicamente utili, poichè fino ad allora la SPESSARTINA era nota solo a livello di specie mineralogica e rarità gemmologica, che non ne giustificava un impiego utile in gioielleria. Quando le nuove gemme africane giunsero sul mercato destarono un notevole interesse, la cosa che potrebbe sfuggire a noi occidentali e che questa colorazione è molto ricercata sui mercati orientali, per il simbolismo connesso con questo colore. SPESSARTINE sono note in giacimenti dello Sri Lanka, Birmania, Madagascar, Brasile, e Australia, come anche da Kenia e Tanzania, ma nessuna di questre mostrava quel colore arancio intensamente brillante ed eccezionalmente bello considerando anche l'ottima purezza delle pietre della Namibia, senza quasi alcuna inclusione visibile ad occhio nudo.
    Ben presto queste pietre divennero l'astro nascente della gioielleria internazionale sebbene vi sia stato qualche marginale disaccordo sulla loro denominazione fra gemmologi e commercianti. Alcuni le chiamavano KUNENE SPESSARTINE dal nome del luogo di provenienza altri le chiamavano HOLLANDINE, ma abbastanza presto il nome di GRANATO MANDARINO si diffuse nel mercato internazionale come ancora oggi vengono chiamate, sfortunatamente il giacimento di Kunene si è esaurito molto rapidamente , o meglio i costi di estrazione e gli investimenti necessari erano troppo alti e la miniera fu chiusa. Fortunatamente il giacimento del fiume Kunene non rimase l'unico. Nel 1994 riapparvero sul mercato delle belle pietre arancioni questa volta provenienti dalla Nigeria ove vennero trovate in una area vicino al confine col Benin , queste pietre sono molto simili a quelle della Namibia ma qualche sottile differenza non sfugge ad un occhio esperto , le pietre nigeriane spesso riescono a superar il carato. A parte il suo stupendo colore arancio brillante, talvolta ha delle sfumature marroni, e variano dal colore di pesca matura fino al più profondo rosso arancio, il GRANATO MANDARINO, ha un notevolmente alto indice di rifrazione che gli conferisce una straoridinaria luminosità , anche in sfavorevoli condizioni di illuminazione una gemma di Mandarino piccola ben tagliata e senza inclusioni brilla vividamente.

    GRANITO (en: Granite grain)

    [Roccia Intrusiva]

    A. Granite. Pin with granite pendant (greatest dimension - ~ 3.5 cm ) that is a tumbled piece of granite from Barre, Vermont region. F.S. Dietrich collection. (© photo by Dick Dietrich) B. Granite from vicinity of St. Cloud, Minnesota (width - 5 cm), that exhibits a typical granitic texture. (© photo by B.J. Skinner) C. Granodiorite bookend (height - 15 cm) presented to Adolph Knopf by his students upon his retirement as Sterling Professor of Petrology at Yale University. R.V. Dietrich collection. (© photo by Dick Dietrich) DESCRIPTION: Granite, is defined by most professional geologists as a phaneritic igneous rock that consists of 20 or more percent quartz, more alkali feldspar than plagioclase feldspar, and between 5 and 20 percent varietal minerals (typically biotite + muscovite + hornblende). A few geologists, who think that at least some granites are not of igneous origin, substitute "igneous or igneous-appearing" for igneous in the just reiterated definition. Properties of the chief minerals, as they occur in granitic rocks, follow: Quartz -- colorless, milky white or smoky (gray-tan); H. 7; S.G. 2.65; transparent to translucent; vitreous luster; conchoidal fracture. Alkali feldspar (which includes microcline, orthoclase and perthite) -- off-white, light tan, salmon-pink to nearly brick-red; H. 6-6½; S.G. 2.55-2.63; subtranslucent to opaque; pearly luster; two good cleavages at or near 90 degrees to each other. Plagioclase feldspar (which in granitic rocks is typically oligoclase) -- off-white to buff; H. 6-6½; S.G. 2.61-2.64; subtranslucent to opaque; pearly luster; two cleavages a few degrees off 90 degrees to each other; polysynthetic twinning -- which is expressed by closely spaced parallel lines that can be seen when certain cleavage surfaces are viewed through a simple (e.g., 10x) hand lens -- is common. As a consequence of the mineral constitutuents, granites have the following overall properties: Colors - typically overall gray or salmon pink to nearly brick red H. (effective hardness) 7 S.G. 2.64-2.65 Light transmission - opaque Luster - ranges from dull to grainy with sporadic parts pearly and vitreous Breakage - irregular Miscellany - In the marketplace, the term granite is frequently extended to include virtually all relatively light colored igneous and igneous-appearing rocks that roughly resemble granite, sensu stricto. -- Most of the other rocks that are so-designated in the market are monzonites and granodiorites, but a few are diorites and syenites according to accepted petrographic nomenclature. A well known example of these marketplace "granites" is the Mount Airy Granite of North Carolina, which in professional petrographic literature should be called a leuco-granodiorite. Definitions of the names applied by petrographers to these other "granites" are given in the GLOSSARY and general relationships among these rocks can be seen in books such as "Rocks and Rock Minerals" by Dietrich and Skinner (1979). Herein, marketplace usage is followed -- i.e., granite is used to include all relatively light colored (overall nearly white, gray, tan, pink and reddish) phaneritic igneous and igneous-appearing rocks that have a typical granularity. All consist largely of one or two feldspars and quartz plus or minus some dark-colored mineral such as biotite (=black mica); H. >6 (= effective hardness); S.G. ~ 2.65. Also, it seems prudent to note that several of these rocks are gneissic. OTHER NAMES: Granite, granodiorite, etc. are widely accepted petrographic designations. Several granite (etc.) masses around the world have been named on the basis of their locations and are shown on geologic maps and referred to in geological reports by those binomial names -- e.g., the Barre Granite of central Vermont, the St. Cloud Granite of eastern Minnesota, and the Clancy Granodiorite, which was named by Adolph Knopf, to whose memory this compilation is dedicated, for exposures in Kain quarry on Clancy Creek, Lewis and Clark County, Montana. Several of the geographically based names of granites (etc.) are also used in the marketplace. In addition, granites (etc.) of certain overall colors or exhibiting certain relatively distinct appearances have been given names that relate to those characteristics, and those names are used along with or instead of the formal geographically based names. And, a few of these rocks have been and continue to be used as gemrocks. Two examples are: Orbicular granite - Typical orbicular granites contain orbicules -- i.e., spheroidal masses the components of which are arranged in roughly concentric layers -- surrounded by a continuum of "normal" granite. The layers consist of concentrations of the major light versus dark components of the rocks. In some orbicular granites, at least some of the orbicules have cores of the "normal" rock. (Figures D & E). Rapakivi granite (also called "Baltic brown") - Typical Rapakivi granites consist of ovoid masses, with chiefly alkali feldspar cores and relatively thin chiefly off-white plagioclase feldspar mantles, within a so-to-speak continuum of "normal" granite. The alkali feldspars in most of Rapakivi granite are salmon colored orthoclase whereas the plagioclases tend to be off-white oligclase; the other common constituents are biotite and/or hornblende. Some petrographers consider these rocks to be porphyries with the feldspar ovoid masses the phenocrysts and the surrounding "normal" granite the groundmass. (Figure F). D. Granite. Orbicular granite boulder (partly sheathed hammer head gives scale) in glacial debris "a few miles to the north of Granite Harbour in South Victoria Land, Antarctica. The dark coronas of these orbicules are recorded as hornblende. (© photo by Bernie Gunn in Geology, Glaciology, Geography & Wildlife of the Ross Sea Region, Antarctic -- www.RossSea.info -- reproduced here by permission) E & F. Granites. Orbicular granite (top) and Rapakivi granite (below) as shown on two stamps of a set of three that depict rocks from famous localities in Finland This set of stamps, the third of which is shown in the MIGMATITE entry, was issued in February 1986. (© photos of stamps by Richard Busch, stampmin.home.att.net) USES: Stones on bolo cord slides and pendants, watch and clock faces, paperweights, bookends, lazy susan turntables, etc. OCCURRENCES: As relatively large igneous or igneoid masses. NOTEWORTHY LOCALITIES: Barre, Vermont; St. Cloud, Minnesota. REMARKS: Origin of the name granite traces back to the Italian granito, which is the past participle of granire, which means to make grainy; Granire, in turn, is from grano (grain) from the Latin granum, said to have Indo-European roots. Its use as a rock name dates back to at least the early 17th century. Three major uses of rocks widely marketed as granites are for ashlar (for both exterior and interior facings), tombstones and other monuments and sculptures. In the literature, several rocks other those mentioned under OTHER NAMES have been called granite, usually with some modifying adjective. Among those I have seen so-labeled are rocks included in the GNEISS and AMPHIBOLITE entries in this book and even BASALT (called black granite), none of which is a granite. So far as the use of granites as decorative stones, the following quotation from the preface to The Marbles and Granites of the World (Grant, 1955) seems noteworthy. "The author was led [to compile the information published in this book because of his] ... realisation of the artistry of the patterns and colouration of almost all the rocks of the earth. [He believes] ... a humble stone will delight the cultured observer even more than the polychrome of far more brilliant objects. [And, consequently] these Marbles and Granites, then, may be regarded ... as pictures, or at least as colour-schemes designed at the dawn of the world. [So,] they are thus not as incompatible as might be thought with Art, the subject of his previous volumes, but an interesting, and to many perhaps a novel aspect thereof." An especially interesting, remarkably detailed ancient sculpture is illustrated in the July/August issue of "Saudi Aramco World" (page 16): It is described as sculpted by "a royal architect ... , made of diorite about 2090 BC, ... [and] found at Girsu, Mesopotamia." Granite (though not as a gemrock) is the state rock of North Carolina; blue granite is the official state rock of South Carolina; and red granite (also not as a gemrock) is the state rock of Wisconsin. SIMULANTS: ***Graniteware (enamelware) - enamel-coated metal (usually iron or steel, rarely tin). All sorts of kitchenware, ranging from cookware and bakeware to tableware (and even bedpans) were made from the mid 1800s well into the 1900s. The enamel was speckled and baked on the metal. Some of the dark gray graniteware items that were speckled with white roughly resemble granite; although other colors, of which there were several, did notl, they too were called graniteware in many quarters. Of the dark gray and white ones that I have seen, those labeled as made by Kemp Mfg. Co. of Toronto, Ontario, Canada resembled granite most closely. None, so far as I have been able to determine was fashioned into anything marketed as granite per se. - [Appearance suffices.]. ***Wedgewood china - one variety has been made that resembles granite - [Appearance - china is a so-to-speak single phase material.]. REFERENCES: No general reference. Grant, 1955.

    GRANITO GRAFICO (en: Graphic Granite)

    [Roccia Intrusiva]
    ( Fr:: graphique granit/pierre hébraïque/ De:: Schriftgranit; Nrw- skriftgranitt)

    A. Graphic granite specimen (greatest dimension ~12 cm) from Berry pegmatite, Poland, Maine. The Hadleigh Collection. (© photo by F.C. Wilda, www.naturesfinestcreations.com) B. Graphic granite cabochon pendant (greater axis of cabochon - 3.0 cm) fashioned by Frederick C. Wilda from rock collected at the Berry pegmatite, Poland, Maine. The Hadleigh Collection. (© photo by F.C. Wilda, www.naturesfinestcreations.com) C. Graphic granite background. Tiled image of polished surface (vertical dimension ~7.5 cm) cut perpendicular to the length of the quartz "rods". (© photo by Dick Dietrich) [See also Figure 27 in the MIMETOLITH file on this web site.] DESCRIPTION: Typical graphic granites consist of nearly parallel rodlike masses of quartz surrounded by feldspar -- see Figure A. The quartz:feldspar ratio in these rocks ranges from about 10:90 to 50:50 -- i.e., the feldspar component is greater in nearly all specimens. Colors - felsdpar "host" may be off white, cream, tan, pink or salmon; quartz ranges from nearly colorless through white to smoky. The feldspar -- typically perthitic, commonly macroperthitic so the volume of the potassium feldspar can be seen to exceed that of the plagioclase - - of virtually all individual specimens comprise single grains. H. 6 (feldspar), 7 (quartz) S.G. ~2.6 -- i.e., 2.574 (feldspar) and 2.65 (quartz) Light transmission -overall subtransparent to opaque Luster - pearly to dull (feldspar), vitreous on fractures (quartz) Breakage - tends to break along cleavage planes of feldspar and/or away from the quartz rods (i.e., so-to-speak freeing them from the surrounding feldspar) Miscellaneous - Appearance, often referred to as an "intergrowth" of alkali feldspar and quartz, is the definitive characteristic. OTHER NAMES: Hebraic pegmatite or Hebrew stone - see REMARKS. Corduroy rock (sometimes corduroy spar) - see REMARKS. Graphic pegmatite - see REMARKS. Runite - see REMARKS. USES: As gemstones -- typically cabochons or free forms -- for pieces such as pendants; spheres (some extremely attractive!); relatively large pieces such as desk sets and bookends. OCCURRENCES: In some, but not all, granitic pegmatite masses and as clasts in, for example, beach shingles and glacial debris derived from those masses. NOTEWORTHY LOCALITIES: So far as its use as a gem rock, none in particular; however, graphic granite should be looked for wherever granitic pegmatites occur -- e.g., in the Piedmont Province of Virginia and North Carolina. Three locations of pegmatites masses where I have found good specimens are: near Pala, San Diego County, California; at Bedford, Westchester County, New York; and near Custer, Custer County, South Dakota. In addition, I have also collected graphic granite pebbles and cobbles, which have been fashioned into pendants, from glacial debris in Michigan and from beaches along northern Lake Michigan and southern Lake Superior. And, some noteworthy specimens in the CMU student collections are labeled as coming from near Ohio, Gunnison County, Colorado. Also, my attention was recently directed to a photograph of an especially fine specimen of graphic granite from the Talacha pegmatite field, which is near the Duldurginsky granite massif in Agin-Buryat Autonomous Okrug -- i.e., about 150 km south of the city of Chita, which is in theTransbaikal region, east of Lake Baikal, Russia (Margarita I. Novgorodova, personal communication, August, 2005). REMARKS: The names given this rock in different several languages are based on the appearance of its isolated quartz rods as seen on surfaces cut perpendicular to their lengths: They roughly resemble letters of cuneiform inscriptions or letters the Hebrew or Arabic alphabets. From an historical standpoint, and interesting petrographically, the term pegmatite -- currently used widely to describe coarse-grained igneous/igneoid (e.g., granitic) rocks -- was originally applied by L'Abbe Hauy to graphic granite (Brongniart, 1813, p.32). Hauy's use is quite understandable when one considers the derivation of the word pegmatite -- from the Greek p??µat meaning “thing joined together or conglutinated” + ite (OED), certainly in allusion to the intimate "intergrowth" of the alkali feldspar and quartz of graphic granite. These "intergrowths" range in size from microscopic to the gemrock material with individual feldspar grains up to several decimeters in greatest dimension and quartz rods up to several centimeters long. The term "intergrowth" is enclosed herein by quotation marks because there is less than a consensus among petrologists as to how these rocks originated: Some consider them true intergrowths -- i.e., that the feldspar and quartz formed as the result of essentially simultaneous crystallization; others conclude that the quartz represents partial replacement of previously crystallized feldspar grains; and others offer other hypotheses or suggest that each occurrence needs to be considered individually and some may have originated one way and others other ways. For those interested in the genesis or geneses of this gemrock, several articles are in geological publications (see, for example, Barker, 1970 and Fenn, 1986). Early use of graphic granite as a decorative stone is shrouded in antiquity. More recently, it was incorporated in the façade of one of the Vitelli family Palaces, built during the late 15th or early 16th century at Città di Castello,Italy (www.salviani.it). Currently, “graphic granite is used by cooperatives and amateur craftsmen as a decorative material” in the Chelyabinsk region of the southern Urals, Russia -- i.e., at the Taiginka graphite deposit (www.fipc.ru) -- as well as by several lapidaries here and there throughout the world . SIMULANTS: None that I have seen or seen described. REFERENCES: No general reference. VanLandingham, 1962, pt.8.

    Grano (en: grain)

    Unità di peso corrispondente a 1/20 di grammo; viene utilizzato particolarmente per diamanti di piccole dimensioni e perle naturali.

    Green Amethyst > Prasiolite



    GROSSULARIA (Granato) (en: Grossular)

    [Granati di calcio e alluminio:Ca3Al2(SiO4)3 - Ps: 3,5 g/cm3- Ir: 1,75]
    • Colore: Verde menta, verde giallognolo, giallo, Arancio, bruno
    • Durezza Mohs: 7
    • Indice di rifrazione: 1.72 – 1.75
    • Densità: 3.65
    • Chimica: Ca3Al2(SiO4)3
    • Cristallo: isometrico o cubico
    • Lucentezza: vetroso, opaco
    • Origine: comune Mali
    • Varietá: Mali Garnet

    Webster (1963); Maddison (1991, p.249) diverse colors -- e.g., translucent, predominantly mottled brownish yellow massive "grosularite garnet." (JADE Simulants).
    La GROSSULARIA è il Granato che presnta la maggior varietá di materiale gemmifero con una amplissima gamma di colorazioni. I cristalli possono avere colorazioni giallo chiare, giallo oro brillante, giallo verdino o addirittura incolori , queste ultime sono dette LEUCOGROSSULARIE. Assomigliano a Berilli, Topazi e Quarzi, ma mostrano Fuochi e lucentezze più vivide. I giacimenti principali sonmo in Africa Orientale, Canada e Messico .
      Oltre la menzionata LEUCOGROSSULARIA altre varietá sono :
    • la HESSONITE
    • e le varietá verdi note come
    • CROMO GROSSULARIA
    • e
    • TSAVORITE
    • il cui colore viene attribuito a cromo e in secon'ordine al Vanadio.
    • L'IDROGROSSULARIA è una varietá microcristallina traslucida.




    Grossular, diopside, vesuvianite rock

    Kamerling & Fryer (1994, p.186) white grossular and green rock from northern Washington (state).



    Gummite

    this yellowish and/or orangy rock -- which has a characteristic waxy luster and consists of diverse combinations (complexes!) of silicates and salts of uranium plus water -- occurs in, for example, pegmatites of the Spruce Pine district of North Carolina and the Ruggles Mine, New Hampshire. By the way, gummite is best described as an "omnibus term." Pough (1996, p.158)

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