56 BESOUKCES OF CALIFORNIA. 



sometimes pretty large. No satisfactory explanation has been 

 given of the fact that placer-gold is usually in particles so much 

 larger than that found in quartz. 



Gold is fine and coarse mechanically — that is, in the size of 

 its particles — and chemically in its composition. Most metals 

 are found in ores, combined chemically with non-m,etallic sub- 

 stances which hide them. The ores have usually neither the 

 color, the specific gravity, the strength, nor the other peculiar 

 features of the metals. Native gold is never found as an ore ; 

 it is always in a metallic form. The reason of this is, that it 

 does not rust on exposure to the air, nor is it dissolved by any 

 of the simple acids. And yet it is never found pure, but always 

 mixed with silver, in nearly all possible proportions. Fre- 

 quently copper and lead are also found in native gold. The 

 amount of other metal in gold is designated by figures of fine- 

 ness, estimated according to thousandths. Perfectly pure gold 

 is 1,000 fine; gold containing one-tenth of its weight in silver 

 is 900 fine; that is, 900 parts in 1,000 are gold, and 100 are 

 silver. In gold 600 fine, 400 parts in 1,000 are of other 

 metal. 



The native gold in California varies in fineness from 500 to 

 990, averaging about 880. One large piece, found at Downie- 

 ville, was 992 fine. In Mariposa, Fresno, and Buena Vista 

 counties, and at Mono Lake and Walker's River, east of the 

 Sierra Nevada, the fineness is very low. The gold of the Col- 

 orado is very fine. In other districts there are great variations 

 in the fineness within small distances. One has gold 900 fine ; 

 another, one hundred yards distant, has gold only 800 fine. 

 Ordinarily, all the gold in a gully or in a river-bar is of the 

 same fineness ; so also all the gold in a quartz-lode is of the 

 same fineness. But there are the same differences of fineness 

 between the gold taken from different quartz-lodes as in that 

 taken from difterent gullies. For these differences there is no 

 satisfactory explanation. 



Let us now run through the list of the principal mining dis- 

 tricts of the state, giving the fineness of the placer-gold of each : 



