sentences:  Gold in Holocene gravels was found in 1850, followed a few years later by hydraulic mining of Tertiary gravels.By 1880, most of the mining had shifted to lode deposits, such as the Empire Mine.Through 1959, the district produced 10.4 million troy ounces (323 tonnes) of lode gold, and 2.2 million troy ounces (68.4 tonnes) of placer gold.