THE MINERALS OF IDAHO 



261 



MALACHITE (288) 



Basic copper carbonate, 2CuO.CO2.H2O. 



Monoclinic. 



Green copper carbonate is one of the commonest of the secondary 

 oxidation products, forming as large or small crusts or masses or 

 as a conspicuous green stain where primary copper minerals have 

 been exposed to the action of atmospheric agencies or meteoric 

 water. Where present in any notable quantity the mineral usually 

 forms globular or botryoidal crusts having an internal fibrous struc- 

 ture and banded green color. It also 

 occurs frequently as aggregates of thin 

 acicular fibers or needles. Where thinly 

 distributed this mineral has great stain- 

 ing power and a rock may be colored 

 a very vivid green by a very small per- 

 centage of copper in this form. Many 

 localities for the mineral are known in 

 Idaho and, while no dependable locality 

 furnishing the mineral in fine specimens 

 in large number is known, occasional 

 good cabinet material has been found in 

 most of the localities mentioned below. 



ADAMS COUNTY 



In the contact-metamorphic copper 

 deposits of the Seven Devils district 

 malachite is second only to chrysocolla 

 in importance as an ore mineral in the 

 oxidized ores. It is especially promi- 

 nent in the Arkansaw-Decorah-Margue- 

 rite, Peacock, and South Peacock mines. 68 



BANNOCK COUNTY 



In the Moonlight tunnel of the Poca- 

 tello Gold and Copper Mining Co. in fig 

 the Fort Hall district, malachite occurs 

 in beautifully radiating groups and in 

 prismatic fibers forming tufts in quartz and in copper ore consisting 

 of bornite largely altered to copper pitch. 



BEAR LAKE COUNTY 



Malachite occurs in the Humming Bird mine in Paris Canyon in 

 the Bear River Range as radially fibrous masses in the oxidized ore. 

 In part the malachite is scattered through a jaspery quartz rock 

 which is stained deep red by hematite. The rock takes an excel- 



69.— C eru site. Crystal 

 twinned on 771(110). lookout 

 Mountain mine 



D. C Livingston and F. B. Laney. Idaho Bur. Miner and Qeol. Bull. 1, pp. 67-83, 1920. 



