CA.TALOQUE OF GEMS. 511 



of which are: Andradrte, a yellow or orange-brown variety. Deman- 

 toid or Uralian emerald^ a grass-green, emerald-green, or brownish- 

 green stone having a brilliant luster, and when cut exhibiting consid- 

 erable lire, especially by artificial light. It is somewhat soft, having 

 a hardness of about 5. Coloi}hoiiite is a brownish-black garnet, char- 

 acterized bv a resinous luster. Melanite is a black to yellow-brown 

 kind. 



The lime-chrome garnet, ouvarovite, is almost invariablj^ a hue 

 emerald green, and is harder than any of the other varieties, ranking 

 nearly 8 in the scale. 



In the trade the lighter-colored clear garnets are often called hya- 

 cinth. The 3^ellowish is thejacinta/ a yellowish-red, the guarnaccino 

 or vermeiUe; the red with a tinge of violet, 7'uhino-di-rocca or grenat 

 syriam. The deep clear red is the true precious garnet and is often 

 called carhimcle. 



Garnet is common in mica schist, hornblende and chlorite schist, 

 gneiss, syenitic gneiss, and granite, occurring also in limestone, ser- 

 pentine, and vokanic rocks. The garnet of granite, gneiss, mica 

 schist, and similar rocks is commonly almandite. Grossula.'ite is com- 

 mon in limestones and crystalline schists. Pyrope belongs especially 

 to peridotites and the serpentines derived from them; occurs also in 

 basalts. Spessartite occurs in granitic rocks, in quartzite, in certain 

 schists, and in some rhyolytes. Iron garnets are common in eruptive 

 rocks, occurring also as a product of contact metamorphism. Deman- 

 toid occurs in serpentine. The chrome garnets belong particularly 

 with the chromite in serpentine; found also in granular limestone. 



GOTHITE. 



A hydrated oxide of iron, which, when occurring in acicular crystals 

 in limj^id quartz, is often cut into gems. The color of the gothite is 

 yellowish, reddish, and blackish brown. 



GOLD. 



Gold, in crystals, filiform, reticulated, and arborescent shapes, or in 

 nuggets, is frequenth' worn as a jewel. Gold penetrating white, black, 

 rose, and amethystine quartz is worked into jewelry of all sorts, the 

 designs often being elaborate. 



GYPSUM. 



ALABASTER — SATIN SPA R — SELEX ITE. 



Gypsum occurs in monoclinic crj'stals and massive. It has a hard- 

 ness of 2, a specific gravity of 2.3, and is usually white in color, some- 

 times gray, flesh red, honey, and ocher yellow, l^lue, brown, and black. 

 Three varieties are recognized. 1. Selenite^ occurring either in dis- 

 tinct ci'ystals or broad folia, which are transparent throughout. It is 



