Geology from a Motor Car 391 



many quarries in operation. The stone for the State Capitol, 

 at Sacramento, and for many buildings in San Francisco, came 

 from Rocklin quarries. The rock is a normal granite com- 

 posed of quartz, feldspar and mica. A short distance from 

 Rocklin the country rock grades into granodiorite, which is 

 the predominant rock in the Sierra Range. Granodiorite differs 

 from granite in that it contains little or no quartz. 



At Loomis there is a large granite quarry, but its most im- 

 portant industry is fruit-growing. The soil is decomposed 

 granite. Granite ledges outcrop on the soil-covered plain. 

 The district is favorable for oranges, which are said to ripen 

 early, and that injurious frosts are almost or quite unknown. 

 Penryn and Newcastle are fruit-growing districts. Pears, 

 peaches and prunes, and also oranges and lemons, abound, and 

 fig trees and palms are also seen. 



Auburn, Former Mining Town, 

 Produces Fruits 



Auburn in the early days was a mining town, built in the 

 valley of a small stream known as Auburn Ravine. In later 

 years the surrounding hills have been settled and fruit-growing 

 has largely taken the place of mining. Two miles west of 

 Auburn is a mining district where gold and silver occur in veins 

 in the granitic rock (granodiorite). Remnants of lava beds 

 are passed through about Auburn, beds which originally cov- 

 ered the granite rocks. 



Gold-Rearing Quartz Veins at Coif ax 



Approaching Colfax yellow soil derived from Jurassic 

 (Mariposa) slates is crossed. Beyond Colfax is a deep ravine 

 up which runs a narrow-gauge railroad to Grass Valley and 

 Nevada City. The ravine opens into the valley of North Fork 

 of American River, cut in Mariposa (Jurassic) slate. In this 

 formation are some of the principal gold-bearing quartz veins 

 of California, including the Mother Lode. Beyond Colfax and 



