Old Mines of Southern California / Desert-Mountain-Coastal Areas Including the Calico-Salton Sea Colorado River Districts and Southern Counties

Desert-Mountain-Coastal Areas Including the Calico-Salton Sea Colorado River Districts and Southern Counties
1965 Frontier Book Company Toyahvale, Texas 79786
Reprinted From The Report of The State Mineralogist 1893 Limited to 1000 copies
By W. H. Storms, Assistant in the Field.
The mining industry in this county is not as extensive as that of some of the neighboring counties, but there are mines in Los Angeles County of unquestioned value, and others which have a prospective value, dependent to a great extent upon the success achieved in working certain base ores, which occur in comparative abundance.
One of the most interesting mines in the county is located in the rugged mountains about 8 miles from the town of Azusa, in the San Gabriel Cañon. It is commonly known as the Kelsey Mine, and has become famous as a producer of silver ore of fabulous richness.
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.