. Appendix to the Journals of the Senate and Assembly of the ... session of the Legislature of the State of California. o ^r 150 REPORT OF STATE MINERALOGIST MICA-SCHIST Mica-schist, talc-schist, amphibolite-schist, pyrophylite and similarmagnesium aluminum silicates are found at various points in the countyas rock-forming minerals in the broad zone of Jurassic and Cretaceousrocks lying between the valley sediments and the granite batholith of theSierra. Certain commercial uses have been developed in recent yearsfor some of these schistose and talcose minerals and research work iscontinually a
. Appendix to the Journals of the Senate and Assembly of the ... session of the Legislature of the State of California. o ^r 150 REPORT OF STATE MINERALOGIST MICA-SCHIST Mica-schist, talc-schist, amphibolite-schist, pyrophylite and similarmagnesium aluminum silicates are found at various points in the countyas rock-forming minerals in the broad zone of Jurassic and Cretaceousrocks lying between the valley sediments and the granite batholith of theSierra. Certain commercial uses have been developed in recent yearsfor some of these schistose and talcose minerals and research work iscontinually adding to the number that may have a special industrialuse. A large undeveloped deposit of pyrophylite occurs at ThreeButtes, about two miles southwest of Indian Gulch, in Sec. 9, T. 6 S., R.]6 E., that may eventually prove valuable. ROCK CRYSTAL Quartz crystals in considerable amount, some of good quality, butmostly of small size, have been found in many of the mines in MariposaCounty. There has been no commercial output, although there is amarket for rock crystal that meets certain specifications regarding White Hock Silica (quartz) Deposit, near i^ewis, Mariposa County. clearness and freedom from flaws, for industrial uses and as a gemmaterial. W. L. Apperson, Mariposa, has taken out several tons fromhis property. SILICA White Rock Silica Deposit is on patented land, owned by J. H. Helmand P. Carmean of Le Grand. The deposit consists of a massive outcropof white glassy quartz, practically pure silica, but with occasionalspots showing a little iron stain. The outcrop is on the top of a knollat an elevation of 1117 feet and is a noted landmark for miles around,being visible from the valley highway. This massive vein occurs nearthe contact of slate on the west and a granite instrusion of almostcircular form. One mile southeast of this exposure there is anothersimilar outcrop, apparently on the same vein but somewhat smaller, SAN FRANCISCO FIELD DIVISION 151 and several pa
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