Gold 305 



slope of the Sierra Nevada Range. The rocks are old geolog- 

 ically, and are much folded, crumpled, and fractured. Much 

 folding, upturning, and crumpling of the rocks occurred before 

 the gold was deposited. The gold of the Mother Lode district 

 occurs both in gravels of overlying formations, the superjacent 

 series, and in veins of the bed-rock. The gravels were first 

 exploited, and this was followed by mining upon the gold- 

 quartz veins. 



What is known as the Mother Lode is a comparatively nar- 

 row belt extending in a nearly northwest-southeast direction 

 along the western foot-hills region of the Sierra Nevada Range. 

 The district is about 6 l /2 miles wide and 70 miles long. It con- 

 tains the principal mining districts of Amador, Calaveras, and 

 Tuolumne counties, and a small part of Mariposa County. It 

 is a vast belt of rocks that has been fractured, and mineral 

 matter deposited from solution in the spaces between the walls. 

 Fractures and filled veins ramify in varied fashion throughout 

 a great belt. Branch veins go off from larger veins, and pinch 

 out and cease, and re-occur in no known definite relation. The 

 boundaries of the Mother Lode region are arbitrary lines. 

 There are other gold-bearing regions both north and south 

 of this belt, but by far the largest quantity of gold has been 

 produced within the limits of what is called the Mother Lode. 



The following description of the Mother Lode is from 

 Julihn and Horton, U. S. Bureau of Mines, Bull. 424: 



"The Mother Lode of California is a zone of rock fracture 

 and mineralization ranging in width from several hundred feet 

 to a mile or more. It is often flanked on each side by a similar 

 zone of lesser width. The lode is characterized by quartz that 

 contains some gold. The quartz occurs predominantly in veins 

 or lenticular masses of limited extent. The zones of fissuring 

 occur in rocks that are predominantly folded sedimentaries of 

 the Calaveras and Mariposa formations, the former being of 

 Carboniferous, the latter of Jurassic age. After the Calaveras 

 was formed a period of metamorphism succeeded that was ac- 



