66 NEW YORK STATE MUSEUM 



a and 5 axes almost equal. Parallel groupings are common as 

 well as massive and columnar forms. The cleavage is nearly 

 cubic in angle. Cryolite is transparent to translucent; colorless 

 or white, often reddish, brownish or black owing to small 

 amounts of iron, and has a vitreous to greasy luster. The Ger- 

 man name EisMem (ice-stone) suggests its resemblance to ice. 

 It is quite soft (H=2.5) and is readily melted in the flame of a 

 candle. 



The principal locality for cryolite is Ivigtut in west Greenland, 

 where it is found in a vein in gray gneiss. 



It is used in several chemical processes, notably in the manu- 

 facture of aluminium. ^ 



Atacamite Cu 2 ClH 3 3 



Atacamite is a hydrated oxychlorid of copper containing 16.6$ 

 chlorin, 14.9$ copper, 55.8$ copper oxid and 12.7$ water. 



Atacamite occurs in orthorhombic prismatic crystals, vertically 

 striated. It is more commonly found in confused crystalline 

 aggregates and fibrous or granular massive forms. The luster 

 is adamantine to vitreous and the color bright to dark green. 



Atacamite takes its name from the Atacama desert in 

 northern Chile where it is found associated with other copper 

 ores; it is also found in Bolivia, South Australia, Cornwall and 

 Arizona. 



It is an ore of copper. 



OXIDS 



OXID OF SILICON 

 Quartz Si0 2 



Quartz is pure silica or silicon dioxid (53.3$ oxygen and 46.7$ 

 silicon). It is often colored by small amounts of iron oxid, man- 

 ganese, titanium, carbon, etc. 



Quartz crystallizes in the rhombohedral-trapezohedral group 

 of the hexagonal system; the crystals are commonly prismatic 

 with the prism faces striated parallel to the basal plane and are 

 terminated by one or both rhombohedrons together with other 

 modifications characteristic of the group. Distortion gives rise 

 to flat and unequally developed forms of great variety as well 

 as acicular, tapering and twisted individuals. Grouping of 

 crystals in parallel position, " scepter," " phantom," and capped 



