314 GEOLOGY OF THE EUltEKA DISTRICT. 



Dr. Hillebraud regards the greater part of the tellurium as occurring 

 in the state of telluric acid, because in boiling with hydrochloric acid much 

 chlorine is evolved, although there is 110 manganese present, and on reducing 

 it with sulphurous acid the tellurium is immediately precipitated. Dr. Hille- 

 brand notes the absence of all sublimation products of tellurium, antimony, 

 and arsenic on heating the ore in an open tube, indicating the previously 

 complete oxidation of these substances. The telluric acid is nearly sufficient 

 in the Lord Byron ore to combine with the bismuth, leaving enough over 

 to combine with the small amount of silver present. Some silver in both 

 ores probably exists in combination with tellurium as a telluride. These 

 ores possessed no commercial value on account of the exceedingly small 

 amount of them obtained. In the case of the ore from the Kelly mine 

 it will be seen that there is a large amount of carbonate of lime present, 

 but it is not possible to say whether this occurred as calcite, a secondary 

 product, or as limestone derived from the country rock. 



Occasional pockets or crevices in the limestone are characterized by 

 the deposition of wad and other compounds of manganese. Silica is rarely 

 found in the fissures and chambers in the Richmond and Eureka mines, but, 

 on the other hand, most of the deposits on Prospect Ridge carry more or 

 less quartz, and associated with it there appears to be, judging from the 

 assay reports, an increase in the amount of gold. Silica also characterized 

 the mines of the Hamburg Ridge, as is shown not only in some of the 

 larger deposits, but in such properties as the Connolly and California mines. 

 Variations in silica present no greater range than other mineral matter 

 deposited under conditions of solfataric action. It is known as one of the 

 most common products from deep-seated sources. The noticeable feature 

 about the silica is not its occurrence on Prospect Ridge, but rather its 

 absence from the Ruby Hill fissure and connecting chambers. 



As has been previously mentioned, the mines of Ruby Hill have 

 yielded up to the time of the present investigation gold and silver to the 

 value of $60,000,000, accompanied by over a quarter of a million tons <>t 

 commercial lead. The large amount of iron contained in the ores has 

 never been estimated. These enormous products of the heavy metals, 

 deposited in small openings in the Ruby Hill limestone, within a very 



