CHAPTER VIII. 



LEAD AND SILVER. 



2.08.01. There are two general methods of extracting silver 

 from its ores, the one indirectly, by smelting with and for lead ; 

 the other by amalgamation, chlorination, or some such process. 

 Hence under silver there are two classes of mines lead-silver and 

 high-grade silver ores. Both have almost always varying amounts 

 of gold. The lead-silver mines furnish also, as noted above, by 

 far the greater portion of the lead produced in the United States. 

 Ores adapted to lead-silver metallurgical treatment form, in gen- 

 eral, the oxidized alteration products of the upper parts (above 

 permanent water level) of deposits of galena and pyrites. They 

 may be well-marked fissure veins, chimneys, chambers, or contact 

 deposits. Ores which of themselves are adapted to other pro- 

 cesses are often worked in with the lead ores, and unchanged sul- 

 phides are artificially oxidized by roasting preparatory to; smelt- 

 ing. The localities are taken up geographically from east to 

 west. 



2.08.02. LEAD-SILVER DEPOSITS IN THE ROCKY MOUNTAIN 

 REGION AND THE BLACK HILLS. The mines are described in order 

 from south to north, beginning with New Mexico. 



NEW MEXICO. 



2.08.03. Example 29. The Kelley Lode. Oxidized lead ores, 

 with some blende, calamine, etc., forming a contact deposit be- 

 tween slates and porphyry. The ore body is in the Magdalena 

 Mountains, thirty miles west of Socorro, and has supplied the 

 Billings smelter at that point. Numerous other ore bodies along 

 the contact between sedimentary and eruptive rocks occur in the 

 same region. 



2.08.04. Example 29a. Lake Valley. Farther south, in Dona 

 Ana County, the mines of Lake Valley afford lead ores on the 

 bedding planes of limestone and along the contact between it and 



