6 SILVER LEAD DEPOSITS OF EUREKA, NEVADA. 



limestone on the slope north of Adams Hill, all the mines which will be 

 discussed in this report are found either in the Prospect Mountain or Ham- 

 burg limestones. No deposits whatever have been found in the Secret 

 Cafion shale which separates these two beds, and although it is true that 

 pyrite, both as impregnations and in masses, as well as distinctly defined 

 veins of quartz accompanied by calcite, has been found in the Prospect 

 Mountain quartzite, the lowest of the sedimentary beds of the district, it 

 has had no economic value. These occurrences moreover do not seem to be 

 in any way connected with the deposits in limestone. As far as is known, 

 there is no ore in the Hamburg shale. 



Quartzite. — The Prospect Mountain quartzite occurs on Prospect Peak, 

 and extends northerly, southerly, and westerly from this point, covering an 

 area of about a square mile. It is also found in the shape of a horseshoe 

 at the northern end of Prospect Mountain, where it divides Ruby Hill, of 

 which it forms the lower western portion, from the main mountain. There 

 is a third small outcrop of this rock on the west slope of Prospect Mountain, 

 between the two above-mentioned localities. These three places are the 

 only ones where this quartzite is found in the district. On the surface it is 

 of a reddish color, which is no doubt due to the oxidation of pyrite, but at 

 a depth of a thousand feet, or at a point where oxidation has not set in, it 

 is of a grayish-white color. It is brittle, particularly near the limestone, 

 where it is often possible to crush it in the hand. It breaks in sharp angu- 

 lar pieces, of which the faces of fracture have a somewhat vitreous appear- 

 ance. Aboveground it is usually harder and more compact. ,It is evi- 

 dently not even approximately pure silica, and is more or less associated 

 with clayey material. 



prospect Mountain umestone. — The Prospect Mountain limestone composes the 

 bulk of Prospect Mountain and Ruby Hill. It was laid down conformably 

 on the quartzite, and to subsequent upheaval and the erosion of overlying 

 formations owes its present prominence on the hill and mountain. Its strike 

 is northerly, following the ridge cf Prospect Mountain until it reaches Ruby 

 Hill, where it bends round to the west, following the quartzite horseshoe. 

 Its dip as exposed by the workings of the Ruby Hill mines is certainly much 

 less than 40°, but owing to the absence in most places of all signs of stratifi- 



