THE ORES. f>5 



throughout the ore. Some of the galena contains considerable molybde- 

 num, but whether the quantity contained in it will account for the presence 

 of the considerable amount of wulfenite in some of the ore is a matter oi 

 doubt, From the manner in which some of it is found surrounding nodules 

 of galena carrying molybdenum, and from its occurrence mixed with the 

 other products of decomposition of that mineral, it is evident that a portion 

 of it at least was formed by the decomposition of the molybdenum-bearing 

 galena. Thus far the existence of molybdenite (sulphide of molybdenum) 

 has not been detected in the oxidized or unoxidized ore. It exists, how- 

 ever, in the underlying quartzite. Several specimens of this mineral were 

 found in sinking the Richmond shaft from the 900 to the 1,200-foot level, 

 also in the cross-cut from the 1 ,200-foot station through the quartzite to the 

 limestone. As it is usually found in the quartzite, it is in a very finely 

 divided state, and were it not for the few exceptional specimens that have 

 been found, its presence would have been overlooked. It is probable that 

 its occurrence in the quartzite is due to secondary causes, and that, like the 

 pyrite, it was not an original constituent of that rock. It is not improba- 

 ble that it will be found in considerable quantity in the unoxidized ore below 

 the water level. 



Pyrite and arsenopyrite both occur in the unoxidized ores, and the for- 

 mer is found in the quartzite and in some of the other rocks of Ruby Hill. 

 Arsenopyrite is not as plentiful in the unoxidized ores as the amount of 

 arsenic in combination with lead in the oxidized ores would lead one to 

 expect, if the theory that arsenopyrite was the original source of the arsenic 

 is correct; but the bodies of sulphurets hitherto discovered have been so 

 few and small that they cannot be taken as representing quantitatively the 

 minerals which originally composed the oxidized ore bodies. Marcasite has 

 been observed in the shale. 



Limonite (hydrated sesquioxide of iron) is the principal component 

 of the Ruby Hill ores. It stains the ore from a light brown to a deep 

 reddish-brown according to the quantity present and the extent of its 

 hydration, and together with mimetite forms the coloring matter of the 

 "yellow carbonate." It is sometimes found compact, but is usually un- 

 evenly distributed throughout the mass of the ore. Pseudomorphs of this 



