48 MINING INDFSTEY. 



on the surface of 200 feet, tapers around the swell of the east wall to about 

 40 feet on the 428 and 535-feet levels, widening again downward to 100 feet 

 at the deepest drifts. The west vein cropped on the surface and continued 

 west and down to 220 feet. 



In the last three sections this west vein has only appeared as a seam of 

 ore in the general quartz-mass with the east ore-bodies. This wide zone of 

 quartz is broken and shattered into blocks, becoming more and more crushed 

 until in depth it assumes the sugary form. On the 328-foot level it is 50 feet 

 wide, dividing toward the surface into three sheets, of which the western, or 

 thinnest, rises 80 feet and ends. The middle one, 23 feet thick, reaches 70 

 feet above the 240-foot level, while the eastern seam ascends to within 150 

 feet of the surface. Through all of the upper workings down, at least, to 300 

 feet below ground, the quartz is stained with manganese oxide. This occurs 

 in a thin coating and lining of the cracks. It is partly of the ordinary man- 

 ganese oxide and partly hard manganese ore. 



The Comstock lode, then, throughout this section, is walled on the east 

 by normal feldspar-hornblende-propylite, which, near the surface, and more 

 especially north of Gold Canon, is earthy and tinted of every ochreous 

 shade of red and yellow. The porphyritic texture is still traceable in the 

 decomposed upper rock and becomes more and more apparent in depths 

 where, below the line of atmospheric oxydation, the rock assumes its normal 

 condition. Stringers of clay and minute veins of quartz thread the wall-rock 

 in the neighborhood of the vein, and, near the 900 and 1,000-foot levels, gyp- 

 sum accompanies the fissures, occurring in fibrous crystalhzations, usually 

 arranged diagonally across the cracks. 



The nature of the west wall is somewhat problematical. Lying west of 

 the west quartz vein, from the Empire to the Crown Point, is a confused mass 

 of propylite and distorted metamorphic rock, fissured in every conceivable 

 direction, and obscured by thermal action. Replacing these rocks in the 

 Belcher, a mass of white propylite comes in contact with the vein and extends 

 indefinitely downward. The western vein extends from the Alpha to the 

 Middle Belcher, terminating from 300 to 500 feet on what is, in fact, the west 

 wall of the lode. Every indication points to the belief that this singular 

 horizontal clay curves downward and joins the east vein. Wherever explora- 



