THE MINERALS OF IDAHO 73 



It occurs in open cavities in the cerusite ores, sometimes in con- 

 siderable amount, notably in the Mammoth, Morning, You Like, 

 Hercules, Poorman, Tyler, Bunker Hill, Caledonia, Sierra Nevada, 

 and other veins. In the Tyler mine coarse aggregates of crystalline 

 wires were attached loosely to cerusite crystals or imbedded in spongy 

 limonite. One small cavity found by the writer in lease workings 

 in 1912 yielded 9 ounces of such wire silver and a similar cavity in 

 the Barney stope on this vein was said to have yielded enough loose 

 silver to fill a nail keg. Delicate frost-like silver was common in 

 the Sierra Nevada mine. In the Bunker Hill ores silver was not so 

 common, but it occurred near the surface in the Blacksmith stope 

 in white cerusite. The Caledonia mine probably supplied as much 

 or more native silver than any other mine in the district. Here it 

 occurred in cerusite and limonite and also as strings and wires in 

 large amount in brecciated and leached white quartzite. Sometimes 

 such quartzite yielded slabs of silver 3 millimeters in thickness and 

 several centimeters in diameter. Thin foil also occurred in narrow 

 cracks in the ores. In soft clayey gouge the native silver was inti- 

 mately mixed with native copper and coarse dendritic wires of copper 

 occasionally had a thin natural outer plating of silver. 20 In the 

 Hercules mine native silver was common in the oxidized ores as the 

 usual fine dendritic mossy aggregates and also in places as coarse 

 wires. Some of the mossy silver was deposited on anglesite crystals. 21 

 In the Yankee Boy mine on Big Creek native silver has been found 

 as irregular hackly masses coated with manganese oxide. In the 

 Snowstorm mine small grains of native silver occurred disseminated 

 in white quartzite with small amounts of malachite. 



WASHINGTON AND ADAMS COUNTIES 



Native silver is reported to occur with horn silver, argentite, and 

 cerusite in veins of the Heath district. 



COPPER (15) 

 Copper, Cu. Isometric. 



ADAMS COUNTY 



Native copper occurs sparingly in the oxidized ores of the contact 

 metamorphic copper deposits particular^ in the South Peacock 

 mine. 



BOISE COUNTY 



Copper has been noted in small amount in oxidized gold ore from 

 the Coon Dog mine, Summit Flat district. 



*> Earl V. Shannon. Economic Geology, vol. 8, p. 565, 1913. 



2i Earl V. Shannon. Proc. U. S. National Museum, vol. 58, p. 441, 1920. 



