CATALOGUE OF GEMS. 527 



The variety wilsonite is ot" a rich purplish-red color and takes a ^-ood 

 polish. Scapolite is usually found in crystalline rocks and in granular 

 i limestone, more connuonly near o-ranite contacts. 



» SERPENTINE. 



, Serpentine admits of a high polish and is often employed as a mate- 



I rial for ornaments, vases, etc. Its hardness is about 4; specific 

 I gravity, 2.5; luster, resinous to greasy; color, dark green, and Idackish 

 green to oil and siskin green, yellow, and white; frequently clouded 

 with green of various shades and occasionally mottled with red. 

 Boirenite is a cream-colored variety resembling nephrite and having a 

 hardness of 5. WiUlainslte is of a rich blackish oil-green color, often 

 having chromic iron disseminated through it, giving it a mottled 

 appearance. Yerde (ottujue is a serpentinous rock used as a marble. 

 It is clouded with green of various shades and is extensivel}' used for 

 indoor ornamental work. 



Serpentine often constitutes rock masses, and as such is the result 

 of the alteration of an igneous rock composed largeh' of magnesian 

 silicates. 



One hundred parts of the mineral contain: Silica, 43.64; magnesia, 

 43.35; water, 13.01. 



SMITHSONITE. 



Smithsonite has a hardness of 5, a specific gravity of 4.45, and a 

 , vitreous to pearly luster. Color, white, often grayish, greenish, and 

 brownish white; sometimes green, blue, orange yellow, brown, and 

 pink. The rich-colored kinds are occasionally cut for cabinet gems. 



Smithsonite is found in beds and veins associated with other zinc 

 minerals, galena, copper, and iron, usually in calcareous rocks. 



One hundred parts contain: Oxide of zinc, 64.81; carlionic acid, 

 35.19. 



SODALITE. 



The fine blue-colored varieties of sodalite are cut cabochon for gem 

 purposes. Hardness, 6; specific gravity, 2.20; luster, vitreous, inclin- 

 ing to greasy. Sodalite is met with in mica-slate, granite, gneiss, and 

 certain eruptive rocks. 



One hundred parts contain: Silica, 37.2; soda, 19.1; chlorine, 7.3. 



SPINEL. 



ALMAXDIXE — BALAS-RUBY — RUBICELLE — SAPPHIRINE — PLEONAST. 



Spinel crystallizes in the isometric system, commonly in octahe- 

 drons. Its hardness is 8; specific gravity al)out 3.65; luster, vitreous. 

 Color, red of various shades, passing into blue, green, yellow, brown, 

 black, and occasionally nearly white. The mineral affords a wider 

 rang§ of color than any other gem. Following the order of the pris- 

 matic hues there are red, orange, yellow, green, blue, indigo, and vio- 



