300 RESOURCES OF CALIFORNIA. 



In quartz mining, the auriferous rock is ground to a very fine 

 powder, the gold in which is caught in quicksilver, or on the 

 rough surface of a blanket, over which the fine material is 

 borne by a stream of water. About two-thirds of our gold 

 is obtained from the placers, and one-third from the quartz. 



A mine is defined in our dictionaries to be ".a subterraneous 

 work or excavation for obtaining metals, metallic ores, or min- 

 eral substances "; but this definition does not apply to our placer 

 mines, which are places where gold is taken from alluvial de- 

 posits. Most of the work is not subterraneous ; it is done in 

 the full light of day. In some of the claims the pay-dirt lies 

 within two feet of the surface ; in others it lies much deeper, 

 but all the superincumbent matter is usually swept away. 



221. Placers. Placer mines are divided into many clas- 

 sifications. The first and most important is into deep and 

 shallow. In the former the pay-dirt is found deep, twenty 

 feet or more beneath the surface ; in the latter near the surface. 

 The shallow or surface diggings are chiefly found in the beds 

 of ravines or gullies, in the bars of rivers, and in shallow flats. 

 The pay-dirt is usually covered by layers of barren dirt, which 

 is sometimes washed, and sometimes left undisturbed, while 

 the pay-dirt is taken out from underneath it by tunnels or 

 shafts. So far as our present information goes, we have rea- 

 son to believe that no gold country ever possessed so large an 

 extent of paying placer mines, with the pay-dirt so near the 

 surface, and with so many facilities for working them, as Cali- 

 fornia. In Australia, the diggings are very deep and spotted, 

 that is, the gold is unevenly distributed, and the supply of 

 water for mining is scanty. In Siberia, the winter is terribly 

 cold during six months of the year. In Brazil, the diggings 

 were not so extensive nor so rich as in this State. Here we 

 have numerous large streams coming down through the min- 

 ing districts, very large bodies of pay-dirt, and a mild climate. 



After dividing placers into deep and shallow, the next clas- 

 sification will be according to their topographical position, as 



