GEOLOGIC GUIDEBOOK ALONG HIGHWAY 49 



[Bull. 141 



sloping ore did not come for 30 years. These last two innovations did 

 much to increase the speed of underground development, resulting in 

 lower gold content per ton, and called for more mill capacity. The gravity 

 stamp was gradually increased in weight from 250 pounds to 1250 or 

 1500 pounds each. Self-feeders, actuated by one stamp in each battery of 

 five, were provided. Before 1870, the foundries of San Francisco, par- 

 ticularly the Union Iron Works, had become recognized as makers of 

 stamp mills and it was in this state that these mills were brought to the 

 high standards that made them the principal means for reducing gold 

 ore for 50 years. Square wooden stems were supplanted in the middle 

 sixties by cylindrical stamp stems of iron fitted with tappets which, when 

 engaged with cams on the horizontal power shaft, lifted and rotated the 

 stamp. Outside amalgamation was provided by long plates of copper, 

 which were first silver plated, then coated with a thin layer of liquid 

 mercury. Rock breakers, such as the Blake crusher, were introduced in 

 California in 1861 to prepare ore for the stamps. The self-feeder, the 

 rock breaker, heavier stamps and increased running speed gave the 

 stamps greatly increased capacity. 



Treatment of Concentrate 



The concentration of the sulphide, which makes up 1 percent to 2 

 percent of most of our gold ores and nearly always carries enough gold 

 to be worth saving, was first made in sluices with riffles, similar to those of 

 the placer miner. In the sixties, Cornish buddies and other European 

 devices were used, and new types of concentrators were invented. In July 

 1867, George Johnston and E. G. Smith patented an endless belt vanner 

 of rubber, set on a slight incline between rollers 8 or 12 feet apart. It was 

 driven slowly toward the upper roller and also had a short, rapid motion 

 sideways. It proved so effective in saving concentrate that it and the 

 similar Frue vanner, perfected in 1878, became standard equipment 

 where stamp mills were used. The chlorination process, previously 

 known in Europe as the Plattner process, for recovering gold from con- 

 centrate, was brought to California and improved to the point where it 

 was widely used until cyanidation was introduced in 1896. 



It will be seen from these side lights that California quartz mining 

 and milling practice drew freely from European methods, which were 

 usually improved and modernized here. The mining engineers and metal- 

 lurgists of this state became so well known for their work that their 

 advice and services were sought when new districts were opened in foreign 

 countries. 



Development of Water Power 



For a long time after quartz mining started, steam engines using 

 wood fuel obtained locally were the principal source of power for mines 

 and mills. The development of large water systems for hydraulic mining, 

 and the increasing cost and scarcity of wood for fuel, led to the use of 

 water power, under high pressure, to operate tangential or impulse 

 wheels. By the middle eighties, nearly all of the principal quartz mines 

 were using Knight, Pelton or Donnelly wheels of the impulse type to 

 supply their power needs. Of the three makes, the Pelton wheel has been 

 most successful, and the Pelton Water Wheel Company is still a going 

 concern in San Francisco, their product being used in later years for 

 generating hydroelectric power. This Pelton wheel is highly efficient, and 

 made possible the introduction of electric power in the mining regions of 

 the West before public utilities had entered the field. 



Development and Use of Hydroelectric Power 



The first recorded use of electric power for the operation of mining 

 or quartz milling machinery in California was at the Dalmatia mine in 

 El Dorado County in February 1890. Water under 112^ feet pressure 

 was delivered to a Pelton wheel 7 feet in diameter, which operated an 

 electric generator of 126 horsepower, and current was transmitted over 

 a line about one mile long to the plant. Pacific Gas and Electric Company 

 has acknowledged its debt to the California miners and the tangential 

 water wheel. It is not too much to say that the company owed its origin 

 to the hydraulic miners and the Pelton wheel. 



BIBLIOGRAPHY 



ANONYMOUS, California's debt to the miner : Pacific Gas and Electric Progress, vol. 1, 

 no. 8,ip. 2, 1924. 



BROWN, J. Ross, Mineral resources of the states and territories west of the Rocky 

 Mountains for 1867 : U. S. Treasury Dept., 367 pp., Washington, D. C., 1868. 



DE GROOT, HENRY, El Dorado County : California Min. Bur. Rept. 10, pp. 169-182, 

 1890. 



LOGAN, C. A., Mother Lode gold belt of California : California Div. Mines Bull. 108, 

 240 pp., 1934. 



JOHNSTON, GEORGE, Brief history of concentration and description of the Johnston con- 

 centrator: In California mines and minerals, pp. 439-441, California Miners 

 Association, San Francisco, 1899. 



