86 NEW YORK STATE MUSEUM 



masses are common. Distinct individual crystals are commonly 

 transparent with an adamantine luster and are colorless or 

 white. Massive varieties are translucent to opaque and have 

 a silky luster which in the earthy forms is nearly dull. The 

 color is white, gray or grayish black. 



Cerussite occurs with other lead minerals and results from 

 the alteration of galena by the action of water charged with 

 carbon dioxid. It is found in many parts of England and in 

 central Europe; also in Pennsylvania, Virginia, North Carolina 

 and in Wisconsin and other lead regions of the northwestern 

 states and in Colorado and Arizona. i, 



It is mined for lead and silver and is used in a direct process 

 for the production of white lead. 



Malachite (green carbonate of copper) CuC0 3 . Cu(OH)„ 



Malachite is a basic carbonate of copper and contains 19.9$ 

 carbon dioxid, 71.9$ copper oxid and 8.2$ water. 



Distinct monoclinic crystals are rare. The mineral commonly 

 occurs in bright green masses and crusts of botryoidal surface 

 and radiating, silky fibrous structure, showing a banding of 

 light and dark green. It is also found in stalactitic forms and 

 earthy masses. The luster is adamantine, silky to dull, and the 

 color bright to dark green. 



Malachite is formed by the action of water charged with car- 

 bon dioxid on other copper minerals. Large deposits are 

 found at Bisbee Ariz, and adjacent regions. It is also found to 

 a considerable extent in Siberia, Chile and Australia and is of 

 frequent occurrence in all deposits of copper ore. 



It is a source of copper and is frequently polished for orna- 

 mental objects. 



Azurite (blue copper ore) 2CuC0.,. Cu(0H) 2 

 Azurite is a basic copper carbonate differing slightly from 

 malachite in composition. It contains 25.6$ carbon dioxid, 69.2^ 

 copper oxid and 5.2$ water. 



Azurite occurs in monoclinic crystals of varied habit and often 

 highly modified. Massive forms sometimes show columnar 

 structure. As an incrustation it often has a velvety luster. It 

 has a vitreous luster and is distinguished by its characteristic 

 blue color. 



