170 



GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



irregularly mingled. The black quartz owes its color to a large amount of 

 included black silver sulphide and other sulphides. 



In this drift southwest of the shaft the vein dips to the northwest at an 

 angle of about 60. 



CONNECTION OF BRANCH VEIN WITH MONTANA VEIN. 



This vein was followed southwest on the strike and downward on the dip 

 to its junction with a larger and more important vein the Montana. At a 

 point a little over 40 feet southwest of the shaft, an incline on the vein went 

 down 38 feet to the Montana vein, while the same junction along the strike was 

 effected at a point over 100 feet southwest of the shaft. The Montana vein 



o PO 20 30 40 so feet 



Pie. 60. Horizontal plan snowing veins and faults on the 100-foot level of the Montana Tonopali. 



strikes at this point generally east and west, and dips north at an angle of 45^ or 

 55, the dip being somewhat less than that of the smaller vein. The junction of 

 the two veins therefore pitches to the northeast at a comparatively low angle. 



HHKCC1ATED STRt'CTUKE IN THE MONTANA VEIN. 



The Montana vein as developed in this level was very strong. It was from 6 

 to 8 feet thick, being rather thicker than the average vein. It showed white 

 quartz with dark-colored portions and had often a brecciated structure. The 

 dark quartz, which contains a much larger amount of black silver sulphides than 

 the light-colored quartz, proves on assay to contain three times or more the 

 value of the white. 



