82 



SILVER-LEAD DEPOSITS OF EE/REKA, NEVADA. 



Amount of silver in the country rock. — Among all the assays of country rock made 

 only one over 50 cents was obtained, and that was in the immediate vicinity 

 of a large ore body, near the sixth level of the Richmond mine. The far- 

 ther from an ore body a sample is taken the poorer as a rule is the lime- 

 stone, as will be shown hereafter when the assays are examined in detail. 

 Fifteen cents in silver is a remarkably high assay to be got from stratified 

 limestone. That rock lying near the shale outside of the main fissure con- 

 tains scarcely more than a trace of the precious metals. Suppose the 



Fig. -'. — Plan of main drift ami cross-drift, 600-foot level, Richmond mine. Scale, 400 feet = l inch. 



calculation made above to be incorrect, and let the possible value of the 

 limestone be reduced to one-half, or 40 cents, this amount would still be 

 very considerably in excess of the average value of even the crushed and 

 most altered rock, and very much greater than the highest assays obtained 

 from unchanged limestone. 



Assays of country rock. — "With a view to determining, if possible, whether the 

 ore was derived from the surrounding limestone, or whether the limestone 

 was impregnated with ore from the ore bodies or the solutions to which 

 they owe their origin, careful assays were made of the limestone on two 

 lines leading up to a large ore body, the lowest portion of which was about 

 30 feet above the sixth level of the Richmond mine. Since these assays 



