Comstock's silver mines were criticized for the way that their share prices were manipulated on the San Francisco stock exchanges, and for the way that insiders skimmed the profits to the detriment of the common shareholders. Insiders used rumors or assessments to drive share prices down, buy up the cheap shares, then spread rumors of large new silver finds to increase prices once more so that they could sell their shares at a profit. Mining company managers also issued contracts to themselves for timber, and water. Ore from the mines was commonly processed by ore mills owned by the company insiders, who were accused of keeping part of the silver they extracted for themselves and refusing to make an accounting.