The Bonanza mine is on the ridge north of Geiser Creek about 5 miles east of Greenhorn. It was discovered in 1877 and actively operated between 1892 and 1907. According to Pardee and Hewett (1914, p. 119), the lower levels were abandoned in 1904. From several adits and a shaft the mine is developed to a depth of 1250 feet. There are about 18,000 feet of workings. The vein, in argillite, strikes N. 550 W. and is nearly vertical. According to Lindgren (1901, p. 701): "The ore body as a whole forms a mass of clay slate traversed by quartz veins and seams of all sizes. The gold is low grade, being about 600 fine .... Something like 70 percent is free, though it is said that as depth is increased more concentrates and less gold are obtained. The concentrates are said to vary from $20 to $60 per ton, chiefly in gold. The average ore is believed to run from $7 to $12 per ton, but lenses of ore 8 to 16 inches wide have been mined which ran as high as $1400 per ton, and several hundred tons are said to have yielded at the rate of $100 in free gold per ton.
"Though the pay streak averages only 5 to 6 feet, it swelled in places to 40 feet by the appearance of a vast number of quartz stringers. "
Pardee and Hewett (1914, p. 120) presented the following statement of production for the period from 1899 to 1904.
The 1901-1904 output amounted to $636,251.16 from 35,638 tones of ore, indicating an average gross value of $17.85 per ton of ore treated.
Source: Gold and Silver in Oregon, State of Oregon Department of Geology and Mineral Industries, 1968