CHAPTER V. 



ORES OF PROSPECT MOUNTAIN AND RUBY HILL. 



Classification of the Prospect Mountain and Ruby Hill ores. The 0T6S of Ruby Hill are to 



be classed under the head of argentiferous-auriferous lead ores. They are 

 of two classes, oxidized and unoxidized, though up to the present time 

 almost all the ores produced by the mines of Ruby Hill have been of the 

 former character, sulphurets being only found in a very few places in a 

 region two or three hundred feet above the water level and in some locali- 

 ties below it. As might naturally be expected, the line which divides the 

 oxidized from the unoxidized ores is not sharply defined, and the transition 

 is a gradual one. 



influence of the water-ievei on oxidation. — In some places where ore is found at a 

 considerable distance below the water-level, it is in an altered condition, 

 which would seem to point to the fact that the present water-level is some- 

 what higher than it has been at some previous time. This is probably the 

 case, as it is not possible that oxidation could have taken place at any con- 

 siderable depth below the surface of the water. The workings of the mines 

 of Ruby Hill have at present reached a depth of over 1,200 feet, the deep- 

 est point being the bottom of the Richmond shaft. The greatest depth at- 

 tained in the old workings of the Eureka is 200 feet higher than the bottom 

 of this shaft. From the lower workings of the Eureka up 200 feet the 

 ground has been flooded for several years. The water rises 150 feet in the 

 Richmond shaft, but remains at that point. From this it will be seen that 

 there is a difference in water-level of 250 feet between the two mines. The 

 surplus water from the twelfth level of the Eureka flows down a winze to 

 the Richmond ninth level, 70 feet below, and finally reaches a permanent 

 level in another winze 180 feet deeper. In the Richmond mine no ore has 

 been found below the ninth level, 900 feet from the surface, so that it can- 

 not be determined with certainty what its mineralogical character may be 

 below the water-level. 



(51) 



