GEOLOGY OF WEST COAST REGION OF UNITED STATES 

 and marble, and even in the extreme west, south 

 of Monterey, limestone of probably Palaeozoic age 

 appears in massive strata, and the Pico Blanco of 

 this region is reported to be formed of massive 

 limestone strata which can not as yet be utilized 

 on account of isolation in the heart of a rugged 

 country. This wide distribution of limestone gives 

 California her practically inexhaustible resources 

 for the manufacture of Portland cement, an in- 

 dustry which is rapidly assuming importance. 



The heat and pressure that accompanied the 

 intrusion of the Sierra Nevada and related batho- 

 liths developed various rock products of economic 

 value, the most important of which are the marble 

 deposits mentioned above. In addition to these 

 is the excellent slate found in the Mariposa slate 

 formation, especially in Mariposa and El Dorado 

 counties of California. The demand for this 

 article, however, has diminished greatly in the last 

 few years. Small amounts of graphite, also formed 

 by contact action, are produced in Calaveras 

 County. 



The rocks of the batholith are of considerable 

 value. Granite is used as a building stone, as rubble, 

 etc., in cement work, and in the construction of 

 roads. The value at the quarries of the granite pro- 

 duced in 1913 exceeded half a million dollars. The 

 gem mines at Pala, San Diego County, distinguished 

 for their beautiful two-colored tourmalines, and 

 beryl, hyacinth, kunzite, etc., are found in pegmatite 

 dikes in the granite. Lithium-bearing mica has 

 been mined at this locality, and sent to Germany 

 for reduction and preparation of salts of lithium. 



The chief contribution of the batholith to the 

 wealth of the west coast, however, was the result 

 of the chemical activity which accompanied and 

 followed the intrusion, and which resulted in the 

 concentration of the major portion of the metallic 

 wealth for which California is famous. The batho- 

 lith is flanked on the west by compressed belts of 

 rocks with a northwestward trend in California, 

 swinging around to the northeast in Oregon. The 

 metallic zones are oriented according to these belts. 

 The groups of gold deposits, as well as the indi- 

 vidual veins, lie, in general, parallel to these direc- 

 tions, as do the copper belts mentioned below. 

 During both late Jurassic and early Cretaceous 

 times the Coast Ranges were intruded by extensive 

 belts of serpentine rocks, which are characterized 

 by mineral deposits of varied character. 



The gold belt of California is the most famous 

 of the mineral zones of the west coast. This con- 



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