 This gold greatly increased the available money in the United States, which was on the gold standard at that time—the more gold you had, the more you could buy.As the easier gold was recovered, the mining became much more capital and labor-intensive as the hard rock quartz mining, hydraulic mining, and dredging mining evolved.By the mid-1880s, it is estimated that 11-million ounces (340 t) of gold (worth approximately US$6.6 billion at November 2006 prices) had been recovered via "hydraulicking," a style of hydraulic mining that later spread around the world, despite its drastic environmental consequences.