THE MINERALS OF IDAHO 393 



Analysis of chrysocolla from Mackay 



(R. C. Wells, analyst) 



Per cent 



Silica (Si0 2 ) 39. 3 



Copper oxide (CuO) 32. 



Water (H 2 0) 18. 7 



Alumina (A1 2 3 ), etc 2. 4 



Lime (CaO) 1. 7 



Zinc oxide (ZnO) 3. 6 



Magnesia (MgO) Trace. 



Total 97. 7 



The analyzed material of the sample was estimated by microscopic 

 examination, to have the following mineral composition: 



Per cent 



Chrysocolla, CaO.Si0 2 .2H 2 87. 3 



Kaolinite, 2Si0 2 .Al 2 3 .2H 2 4. 5 



Opal, Si0 2 .nH 2 0. (3.85 per cent H 2 0) 8. 2 



Total 100. 



The kaolinite occurs as films along microscopic cracks. The 

 associated opal is bluish and contains some copper. The water 

 content of the chrysocolla was found to vary widely. The chrysocolla 

 is often in large masses and grains of the green silicate are often 

 intimately associated with copper pitch ore. 



LATAH COUNTY 



Some chrysocolla occurs associated with copper pitch and other 

 secondary copper minerals in oxidized copper ores from the Mizpah 

 and other claims of the Hoodoo district. 



LEMHI COUNTY 



Chrysocolla has been noted as an oxidation product of chalcopyrite 

 in the ores of the Copper King mine on Copper King Mountain in 

 the Eureka district. 4 



ONEIDA COUNTY 



Old specimens in the National Museum (Cat. No. 51870, U.S.N. M.) 

 labeled Cariboo mine, Cariboo district, Oneida County, contain 

 waxy blue-green to olive-green masses of chrysocolla up to 5 cm. in 

 diameter. These include grains of chalcopyrite. 



SHOSHONE COUNTY 



Chrysocolla occurs occasionally in many places in the Coeur 

 d'Alene district in small amounts as a secondary copper mineral. 

 It is less common than malachite in the oxidized lead-silver ores. 



* J. B. Umpleby. U. S. Geol. Survey, Bull. 528, p. 76, 1913. 



