The following data is extracted from Baker County, Oregon, Gold Mining History.
About four miles southeasterly of Robinsonville is situated the famous Bonanza mine, the largest and probably most valuable free gold mine of the northwest. Discovered and located in the seventies. It was worked by the original locators for ten years, they reducing the ores by the arrastra process. In 1885 Portland capital purchased it, and erected a ten stamp mill. They continued operations for two years, but failed to make a success of it, and finally closed down. In 1891 the Geiser Estate purchased it, reopened the old works and have had the mine and mill in continuous operation since, and it is today the heaviest producer in the state. They have made a number of substantial improvements, consisting of a twenty stamp mill, saw mill, boarding houses, store buildings, offices, wire tramway connecting mine and mill, &c. At the present writing they have enough ore in sight to run their plant for 20 years, yielding from $8 to $20 a ton, the total mining and milling cost of it being but $2 per ton. Its regular monthly clean-up runs from $20,000 to $22,000, or $250,000 a year. The Bonanza, as well as a number of other valuable properties, including the Greenhorn, Hidden Treasure, and others, are the property of the Geiser Company, composed of Miss Louses Geiser, Mrs. Emma Pullman, Albert Geiser, Ed. Geiser and Frank Geiser.
Source: Baker County, Oregon, Gold Mining History