The Ontario silver mine is a mine near Park City, Utah, United States. It was purchased by George Hearst through R C Chambers from prospectors for $27,000 in 1872.
Hearst and his business partners James Ben Ali Haggin and Lloyd Tevis owned this mine and constructed the necessary infrastructure to make it productive, including hoists and stamp mill. The mine was not profitable for its first three years. According to legend, expenses of development substantially drained Hearst's financial resources. As a result of his straitened circumstances, Hearst sold his home and horses, and even dismissed his servants and enrolled his son William Randolph Hearst in public school. Chambers, who had been retained as manager, brought the bonanza ore body into production by the late 1870s. It eventually produced fifty million dollars' worth of silver and lead.
By the time of Hearst's death in 1891, the Ontario mine had paid him more than $12 million in dividends. This was only one of the four big mines he had brought in in the West, including the Ophir on the Comstock Lode, the Homestake Mine (Nevada), and the Anaconda Copper Mine (Montana). The mine also made manager Chambers one of Utah's Bonanza Kings.
The Ontario mine was credited as being more consistent in yielding annual dividends during the late nineteenth century than any other mine in Utah. The Ontario company's mill was also the birthplace of two significant hydrometallurgical processes, the Russell Process and the Cyanide Process. Edward H Russell (Yale 1878) developed his process for working low grade silver ores by a leaching process, 1883-1884, and young Louis Janin (UC Berkeley) experimented with cyanide on the ores, filing a caveat to patent a cyanide process in 1886.