22 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



ter of the ore will change and cease to be free milliug. lu some cases 

 the ore simply becomes a roasting-milliug ore ; iu some it may become 

 a silver-lead smelting ore, and iu others metals occur with the silver 

 requiring a special treatment, while in others it may become so refrac- 

 tory that its silver (vin no longer be extracted to advantage. 



In many cases ores that are called free-milling contain silver that will 

 not amalgamate, and frequently in such cases the tailings from the pro- 

 cess contains enough silver to be reworked by other processes. Some- 

 times ores containing the metal partly in a condition to amalgamate and 

 partly not are treated as if none of it would amalgamate. 



To illustrate the occurrence of strictly free-milling ores thirteen 

 specimens are shown : 



(1) Free silver, in fiue wire and moss, and sulphides, especially galena and blende, 

 in calcite. Santa Domingo Mine, Batopilas, )4exico. (64959.) 



(2) Free silver, in a mass of blacli decomposition products, iu quartz stained by iron 

 and copper. Arizona Mine, Buena Yistadistrict, Humboldt County, Nevada. (15620.) 



(3) Silver and cerargyrite, in fossiliferous sandstone, the silver being more or less 

 intimately associated with the fossils; commonly called silver-bearing sandstone. 

 Kich ore. Barbee and Walker Mine, Silver Reef district, Washington County, Utah. 

 (55322.) 



(4) Cerargyrite. in small specks in siliceous sandstone. Rich ore. Stormont Mine, 

 Silver Reef district, Washington County, Utah. (55333.) 



(5) Cerargyrite, in thin but large flakes on limonite. Mount Diablo Mine, Colum- 

 bus district, Esmeralda County, Nevada. (15637.) 



(6) Cerargyrite, in small flakes scattered through quartz stained by decomposition 

 products. Mineral Hill Mining Company, Mineral Hill district, Elko County, Ne- 

 vada. (15325.) 



(7) Siliceous limestone, containing the silver as cerargyrite. Eberhart and Aurora 

 Mine, White Pine district. White Pine County, Nevada. (15660.) 



(8) Limestone and quartz, showing stains of decomposition from copper minerals, 

 containing the silver as cerargyrite. Eberhart and Aurora Mine, White Pine district, 

 White Pine County, Nevada. (65317.) 



(9) Limestone and quartz, showing stains of manganese; a frequent associate of 

 free-milling ores. Eberhart and Aurora Mine, White Pine district, White Pine County, 

 Nevada. (65318.) 



(10) Quartz, st.iiued by lead and iron decomposition products. Northern Belle Mine, 

 Columbus district, lOsmerelda County, Nevada. (1.5631.) 



(11) Quartz, stained by lead and copper decomposition i>roducts. Brown's Hope 

 Mine, Lida Valley district, Esmeralda County, Nevada. (15.578.) 



(12) Quartz, stained by lead decomposition ])roductsand containing a little galena; 

 also stained by carbonate of copper. Star Mine, Mineral Hill district. Elko County, 

 Nevada. (15326.) 



(13) Quartz, stained by lead, copper, and iron decomposition products. Tipton 

 Mine, Columbus district, Esmeralda County, Nevada. (15633.) 



To illustrate free-milling ore requiring the use of chemicals, twelve 

 specimens are shown : 



(1) Qnartz, containing sulphides more or less decomposed. Belmont Mine, Phila- 

 delphia district, Nye County, Nevada. (1.5366,) 



(2) Quartz, containing sulphides more or less decomposed ; showing stains of cop- 

 per. Little Bonanza Mine, Cope district, Elko County, Nevada. (15817.) 



