184 S1LVEE LEAD DEPOSITS OF EUREKA, NEVADA. 



the quartzite and shale. As yet no ore of any kind has been found in it. 

 Its peculiarities are very characteristic, and it is easily recognizable wher- 

 ever found. 



The jackson faun. — The main fissure joins a fault which Mr. Hague has 

 called the Jackson fault, somewhere near the American shaft. 



ORES OF EUREKA DISTRICT. 



Minerals. — The following minerals have been noticed in the ores of 

 Eureka District: Galena, anglesite, cerussite, mimetite, wulfenite, limonite, 

 calamine, smithsonite, calcite, siderite, aragonite, quartz, steatite, blende, 

 pyrite, arsenopyrite, molybdenite, malachite, azurite, and wad. The lead 

 minerals are well represented, and it is highly probable that most of the 

 known varieties exist in greater or less quantities in the ores, although the 

 presence of all of them has not been detected. Antimony is present in 

 many ores, but in what form has not been determined. Silver and gold 

 are present; silver in the form of chloride and sulphide, and gold prob- 

 ably in the metallic state. Down to the somewhat irregular water-line the 

 ores are substantially oxidized, and consist mainly of lead carbonate and 

 sulphate carrying precious metals, and accompanied by ferric hydrate. The 

 average tenor is 15 per cent, lead, 0.079 per cent, silver, 0.00248 per cent, 

 gold. Quartzose ores are rare, but when found are important as a flux for 

 the ordinary basic variety. The various classes of ores recognized by the 

 miners are described in Chapter V., but may be omitted here. 



classification of the ore deposits. — The ore deposits of Eureka District, though 

 they contain gold, can be classed under the head of silver-lead deposits in 

 limestone. The type of deposits to which those of Eureka belong is one 

 often met with in the older limestones of the Great Basin, and although 

 these particular deposits have been of more value and are more widely 

 known than any of the others, and exhibit some very interesting structural 

 features, they cannot be said to form an isolated class. 



The lead deposits of the Great Basin in general, and those of Eureka 

 in particular, have some points in common with all the known varieties of 

 lead deposits in the world, but the resemblance is not sufficient to allow 

 any one of these to be taken as a prototype of those of Eureka. As re- 



