The country is made up almost entirely of metamorphic rocks, having schistose, gneissoid, and massive structure. Both hornblende and mica occur in these rocks abundantly, the former being frequently altered to chlorite, or by further change to epidote. Dikes of porphyritic rock have been intruded into the crystalline schists. In the immediate vicinity of the Kelsey vein are intrusions of a dark green, much decomposed, and shattered rock, probably diorite. Faults, great and small, are numerous throughout the region. Within a few hundred feet of the mine is a great fault, which may be plainly seen cutting the mountain. The displacement must reach many hundreds of feet. It has resulted in bringing in contact on a horizontal plane rocks of entirely different character. On the south side of the fault the rocks are made up of quite regularly bedded micaceous sandstones, more or less schistose, and having a prevailing buff or light gray color. These rocks dip east at an angle of 20° to 30°. On the north side of the fault the rocks are harder, of a dark gray color, and containing considerable hornblende. These rocks are more gneissoid and massive than schistose. The dip is much less regular than on the south side of the displacement. Large, lenticular masses of quartzose and feldspathic rock are of frequent occurrence in the hornblende gneiss, evidently the result of the segregation of the contained minerals. On the whole there is much more evidence of the disturbance on the north side of the fault than on the south side. It is in this area of greatly disturbed strata that the Kelsey vein has formed. The vein is of the fissure type and occupies the line of a fault plane, that at first, perhaps, was a mere crack, but which has become enlarged by the movement upon themselves of the rock masses forming the walls, resulting in a grinding and crushing of the rocks by the attrition and pressure incident to this movement. Into this crevice mineral waters found their way, carrying in solution the minerals now constituting the vein. [Illustration: _FAULTING AND TORSION OF THE KELSEY VEIN_] _The Ore._—The silver occurs as native and as glance (argentite), possibly partly as chloride and in combinations with sulphur, cobalt, and arsenic. The associated minerals are cobalt bloom (erythrite), a hydrous cobalt arsenate, nickel arsenate (annabergite), carbonate and silicate of copper (chrysocolla), iron oxide, and black oxide of manganese in a gangue of baryta (heavy spar), with calcite (lime spar) and some quartz. A clay selvage usually separates the vein material from the wall, this feature being well developed in places on the foot wall side, as though open crevices had occurred and the finely divided material which was carried by the percolating waters had found a resting place when an open space was reached, the absence of any current permitting the material to settle.