MIZPAH VEIN. 



123 



especially under the microscope. A slight copper stain has been reported on the 

 ore, but the writer has never seen any. Ruby silver and argentite sometimes occur 

 on cracks, but as a rule these minerals, if present, are not visible to the naked eye. 



Scale 

 o 5 io 15 20 ?5 feet 



Fio. 23. Horizontal sketch plan of portion of the Jlizpah vein in slopes east of Lease 52, about 70 feet from surface, 



showing probable compensating faulting. 



FIG. 24. Reproduction of drawing of model, showing the principal postmineral fractures and faults observed in the 

 Mizpah mine workings. The strikes of these fractures have been plotted through a center point on the top of the 

 cube, and the intersection of the fractures with the other faces of the cube has been drawn. The endless variety of 

 patterns which are made by the same systems of fracturing by their intersection with different planes is here shown. 

 A, Front view of block, looking down. B, Rear view of block, looking up. 



Black manganese oxide is frequent and often concentrated in little vugs. Iron oxide, 

 the result of the alteration of pyrite, occurs, and sometimes pyrite itself, but this 

 mineral is much less abundant in the veins than in the wall rock. 



