TONOPAH EXTENSION MINE. 181 



having the same relation to the chloride as does the sulphide. This black sulphide 

 may be either argentite or stephanite. 



This quartz vein is much broken, so that the general strike and dip could not 

 l)e determined. It may very well be the extension of one of the veins developed 

 in the Montana Tonopah." 



As usual in other parts of the camp, the Tonopah rhyolite-dacite in the 

 Midway contains a number of quartz veins which, however, are irregular, non- 

 persistent, and faulted, and are usually barren. The most important vein of this 

 class was encountered on the 535-foot level, a short distance south of the shaft. 

 This shows several feet of quartz, striking in a west-northwest direction and having 

 a steep dip. On the southeast this vein becomes irregular and passes into barren, 

 cherty quartz, which in turn disappears, turning to silicitied rhyolite-dacite. 

 Most of the vein is barren, but at one point 400 tons of ore, having a value of 

 $30 to the ton, were taken out and milled. A winze follows this vein to the lower 

 contact of the rhyolite-dacite with the earlier andesite, a short distance above the 

 635-foot level. The silicitication and the vein, however, cease at the rhyolite- 

 dacite contact and do not enter the earlier andesite, into which the rhyolite-dacite 

 is intrusive. 



A second vein, having an east-west course, was encountered about 50 feet north 

 of the shaft on the 535-foot level. It dips about 65 to the south and is termi- 

 nated on the east by a fault, so far as explored. It is about 2- feet in thickness 

 and contains a little good ore, of which a few tons have been shipped; the rest 

 of the vein is barren. About 150 feet north of this last-named vein, on the same 

 level, there is smother 2-foot vein of white barren quartz, which has a west-south- 

 west strike and a" northerly dip of 80. This contains no ore, but only white, 

 barren quartz, although assays of from $20 to $30 can be had. 



That these veins are nonpersistent is shown not only by the developments 

 upon this level, but by the fact that they are not found in the same formation 

 on the 635-foot level 100 feet below. Although this level runs through 650 feet 

 of rhyolite-dacite it encounters no strong and definite veins. 



TONOPAH EXTENSION MINE. 

 CONTACT OF EARLIER AND LATER ANDESITE8. 



The Tonopah Extension shaft starts in the later andesite and extends down about 

 183 feet to the contact of the earlier andesite (see fig. 71). This contact is marked 

 by 1 to 2 feet of soft, decomposed rock, and is very flat. Below it the earlier 

 andesite is ^ ory full of quartz veinlets. This phase of the earlier andesite resem- 

 bles in many places some of the phases of the later andesite, although just below 



aSince the writer's visit more ore hu.s been fouud'in the Midway, in a drift at about this level. 



