THE MINERALS OF IDAHO 191 



are octahedral in form but the larger exhibit small faces of the cube and 

 rhombic dodecahedron. Some of them are moderately elongated. 



LATAH COUNTY 



Cuprite occurs in the shallow oxidized zone of the Mizpah deposit, 

 Hoodoo district, associated with malachite, azurite, chrysocolla, 



etc. 92a 



LEMHI COUNTY 



Cuprite occurs in oxidized ore from the Indian Claim, Blackbird 

 district, as grains in quartz. These show good cleavage and are 

 surrounded by malachite and chrysocolla. Fine grained and massive 

 forms are also found in a few parts of the Copper Queen and Copper 

 King mines, and in the Patterson district. 93 



SHOSHONE COUNTY 



Much of the oxidized ore formerly mined in the Snowstorm mine 

 near Larsen, above Mullan, Coeur d'Alene district, contained cuprite 

 with malachite and iron oxides. 



Cuprite was common in the rich silver-copper ores of the upper 

 levels of the Caledonia mine worked through the old shaft west of 

 Wardner. The cuprite was the first product of the decomposition 

 of tetrahedrite. Where tetrahedrite was oxidizing in a matrix of 

 porous quartzite, beautiful specimens were commonly found showing 

 residual cores of tetrahedrite surrounded by concentric rings of 

 cuprite, azurite, malachite, and chrysocolla. Porous masses resem- 

 bling coke were common in parts of the ore. These were brilliant 

 gray with sparkling metallic luster, gave high returns in silver, and 

 had a red streak. For these reasons they were commonly called 

 ruby silver ore, but all of those examined were cellular tetrahedrite 

 mixed with minute and brilliant crystals of cuprite. No reliable 

 specimen of ruby silver has been seen from this mine. Massive 

 granular and spongy cuprite also occurred in the ore, and cavities in 

 the cuprite masses often contained minute grains and filiform wires 

 of native copper. Distorted and much flattened crystals of cuprite 

 were found in cracks. These are chiefly octahedral in form and 

 reach a maximum of about one-fourth of an inch in diameter. They 

 are deep red and transparent with submetallic luster. Numerous 

 specimens of rusty limonite-stained quartzite found on the 500-foot 

 level about 1915 are spangled with minute transparent deep red 

 cuprite crystals associated with cerusite crystals on a velvety layer 

 of limonite. These are very perfect, the predominating form being 

 the octahedron, with or without small modifying faces of the cube 

 and dodecahedron, the form being as illustrated in Figure 33. The 

 following measurements, which were made on a crystal taken from a 



e2 ° D. C. Livingston and F. B. Laney. Idaho Bur. Oeol. and Mines, Bull. 1, p. 95, 1920. 

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



