52 SILYEK-LEAD DEPOSITS OF EUEEKA, NEVADA. 



It will be noticed from a reference to the actual water-level line marked 

 on the elevation (Plate III.) that it is very irregular, showing that there is 

 not everywhere a free circulation of water between the extreme workings 

 on the mineral zone, as well as that the water-level at the northwest end is 

 very much below that at the southeast. The irregularity in the character 

 of the ore in the neighborhood of the present water-level is no doubt due 

 to the rise and fall of the water at different periods, and to the nature of 

 the ground, which in some places is more accessible to the action of the air. 



Local differences in the Ruby Hiii ores. — Although there are some slight local differ- 

 ences in the ores produced by the mines of Ruby Hill, they are so incon- 

 siderable that it is not necessary to describe them by localities, and although 

 their variety is very great, yet the different oxidized ores do not seem to be 

 confined to any one level or any particular chute of ore, but occur indis- 

 criminately at all depths. Sulphurets, particularly galena, are found to 

 some extent intermingled with the oxidized ores, but those represent mere 

 remnants which have escaped oxidation and are usually insignificant in 

 quantity. Masses of sulphurets occur only below or near the water-line. 



Minerals occurring in Ruby Hiii. — Before describing the different varieties of ore 

 found in the mines of Ruby Hill, it may be well to mention the minerals 

 of which they are composed. It is very possible that other minerals than 

 those which are given in the following list occur, but as their presence has 

 not been detected in the careful examinations which have been made of the 

 ores, it is not likely that they exist in any great quantity, or that they are 

 very numerous. 



The galena is usually of a medium grain, and more or less mixed 

 with sulphate of lead. It occurs in the form of nodules, which are 

 changed at the surface into sulphate and carbonate of lead, and in irregu- 

 lar masses distributed throughout the ore. It is often of a dull black color, 

 owing to the admixture of sulphate, and contains small quantities of arsenic 

 and antimony, and in some cases molybdenum, which is probably in the 

 state of sulphide. It usually carries from $100 to $150 per ton in silver and 

 from $1 to $10 in gold. It is richer in silver and poorer in gold than the 

 average ores. Pseudomorphs of galena after other minerals, although they 

 may exist, have not been noticed. This fact renders it improbable that any 

 sulphide of lead has been deposited since the period of oxidation. 



