GUIDE TO THE MINEUtALOQIC COLLECTIONS 93 



Diallage. A foliated variety, green or brown in color. 



Pyroxene is an essential constituent of many basic eruptive 

 rocks notably the diabases and gabbros. It occurs associated 

 with amphibole, wernerite and the feldspars. In New York 

 pyroxene occurs in handsome specimens in Orange, Westchester, 

 Essex and Lewis counties and specially in St Lawrence county. 



Spodumene LiAl(Si0 3 ) 2 



Spoduinene is a silicate of lithium and aluminium. 



It occurs in monoclinic crystals sometimes of considerable size 

 which are characterized by a lamellar structure parallel to the 

 orthopinacoid causing them to split into broad smooth plates. 

 In the variety hiddenite the crystals are small, transparent and 

 of a yellow-green or emerald-green color. It is also found in 

 cleavable masses. The luster is vitreous and sometimes pearly 

 on the cleavage surfaces, and the color white or various shades 

 of green, pink and purple. 



Spodumene occurs in granite rocks and is readily altered. 

 Immense crystals are found at Branchville Ct. The variety hid- 

 denite occurs at Stony Point N. C. 



The emerald-green hiddenite is used as a gem. 



Jadeite (jade) NaAl(SiO : ,) 2 



This is a tough translucent mineral of closely compact struc- 

 ture and of a general green color. It is chiefly notable as the 

 material from which many of the prehistoric implements were 

 made and is still used in the East, specially in China, for orna- 

 ments and utensils. 



Wollastonite (tabular spar) CaSi0 3 



Wollastonite is a silicate of calcium, sometimes occurring in 

 tabular monoclinic crystals, but usually in cleavable to fibrous 

 white or gray masses. When fibrous the fibers lie in parallel 

 position or are arranged in reticulated bundles of parallel 

 fibers (pi. 29;,). The luster is vitreous to silky and the color 

 white or faint tints of gray, yellow, red or brown. 



Wollastonite is found in granular limestone ;ui<l as a contacl 

 mineral. 



