214 



GUIDEBOOK OF THE WESTERN UNITED STATES. 



Rocklin. 



Elevation 219 feet. 

 Population 1,026, 

 Omalia 1,671 miles. 



Rocklin^ also in the fruit belt, is the principal granite-producing 

 locality in California, whence its name. In the vicinity of the town 



20 or 25 quarries are in operation, and some of them 

 may be seen from the railroad. The first quarry was 

 opened in 1863, and the stone was used in construc- 

 tion work on the Central Pacific Railway. The stone 

 for the State Capitol at Sacramento (PI. L, p. 216) and 

 for many buildings in San Francisco came from Rocklin.^ 



Tlie traveler has now practically reached the Great Valley of 

 California. The country spreads out to the north and south in low 

 undulations and ahoad are plains as far as the eye can see. 



The great gold-dredging fields of California he along the belt of 

 country where the Sierra slope merges into the valley plain, but 

 none of these fields is crossed by the Overland Route. One pro- 

 ductive district is near Folsom, about 10 miles south of Rocklin, on 

 American River. This district produced gold to the value of 

 $2,498,603 in 1913. The MarysviUe dredging district, on Yuba River 

 about 30 miles northwest of Rocklin, produced $2,420,455 in 1913, 

 and the Orovillc district, on Feather River about 25 miles north of 

 Marysville, $1,918,050. The gold is obtained by powerful electri- 

 cally driven dredges— -huge floating scows, some of them 150 feet long, 



provided with great buckets, linked together in an endless chain, for 



scoopmg up the gravel and with complete machinery for screening 

 and wasliing the gravel and recovering the gold. Once floated in a 

 pond the dredges dig their way through fields, vineyards, and 

 orchards, filling in behind them with washed gravel. The gold was 

 brought down from the slopes of the Sierra and deposited in recent 

 geologic time by the rivers near which the dredges are working. 

 Of late years the hard bowlders left by the dredging have been 

 crushed and utihzed as broken rock for road building. Some effort 

 has been made also to restore the dredged ground to arable condi- 

 tion. Wliere this has been successfully accomplished in the Sacra- 

 mento region vineyards and olive groves occupy areas from which 

 gold and road metal have been mined. 



At the west base of the Sierra, but not continuouslj^ exposed all 

 along it, are beds of brown Upper Cretaceous sandstone (Chico for- 

 mation) and of Ughter-colored Eocene sandstone and clay, containing 

 thin coal beds (lone formation) .^ All these beds are younger than 



^ The rork is of light^ray color and of 



medium fine 



gram, ijrrayisli quartz 

 graliis, "white feldspars, black or dark- 

 hrown hiotite, and silvery mii9co\ite in 

 small scales may be readily dktingnished 

 with the unaided eye. In composition 



the rock is a normal granite, but a short 

 distance from Rocklin the coiintr>^ rock 

 grades into a granodiorite. 



^ The lone formation has been described 

 as Miocene, but recent investigations in- 

 dicate that it is Eocene. 



