REPORTED TIN DISCOVERIES.
Frequently there have been rumors of the discovery of tin stone in San Diego County, but up to this time no such ores are known to exist outside of the property known as the Temescal Mines, which are located on the line of San Bernardino and San Diego Counties. However, in the large crystalline area which extends over a considerable portion of San Diego County, it would not be strange to find tin stone under conditions similar to those which obtain in the Harney Peak region in the Black Hills of Dakota. There the cassiterite is found in good-sized crystals and finely disseminated grains in a matrix of coarse-grained granite, which has been thrust up through the schists in the form of intrusive dikes of greater or less size. It usually is associated with tourmaline, wolfram, and other black minerals, making it difficult to distinguish it without making a test of some sort. The search for tin in San Diego County has been confined to looking for a black rock similar to that found in the Cajalco Mine.