MONTANA TONOPAH MINE. 



171 



Examination of the breccia shows that frequently the black quartz occurs as 

 angular fragments cemented by the white, while in other places, perhaps in the 

 same exposure of the vein, fragments of the white quartz are cemented by the 

 darker and richer ore. The whole is a solid, substantial vein, both dark and 

 white quartz having every mark of primary origin. The only trace of movement 

 is in the brecciation of the dark and white quartz, as above described. 



PIG. 61. Figure drawn from sketch, showing face of ore of the Montana vein on the west drift, 460-foot level, 

 Montana Tonopah mine. To illustrate fissure with crustified high-grade ores, subsequent to the formation of the 

 ordinary veins, but within the period of primary ore deposition; a, altered andesite, wall rock; b, main Montana 

 vein of ordinary type; c, subsequent fissure filling. Within this the dark streaks are rich black sulphide layers, 

 with quartz and carbonates between. In the central quartz band are druses lined with adularia crystals. 



CBD8TIPICATION IN THE MONTANA VEIN. 



Another allied peculiarity of this vein, as compared with other veins of the, 

 district, is that portions are regularly banded or crustified. 



Such crustification is not characteristic of the whole vein, for the crustified 

 portion occurs surrounded by solid quartz possessing no banded or comb structure 



