Mining
His scientific eligibility led him to be invited by cotton manufacturer Colonel William Reynolds to search for mining areas in the West. The greater salary enticed him to journey West. Hill traveled to Colorado in the spring of 1864 to investigate mineral resources. In his search, he traveled alone and with fellow scientists and entrepreneurs. He returned home to Providence after having accomplished little, where he officially resigned from his teaching position and vowed to devote the rest of his life to the search for gold.
Upon his return to the West, he bought several gold mines, but soon ran into financial difficulties because the smelting techniques at the time were resulting in low yields. The Sterling Gold Mining Company and the Hill Gold Mining Company were established around Central City in Colorado. The preferred method of extraction in those days was stamp milling. A stamp mill consisted of heavy iron blocks attached to wooden or steel rods that rose and fell in accordance with a horizontal beam. After the ore containing the gold was crushed sufficiently, the resulting dust was run over copper plates containing mercury, which formed an alloy from which the gold could be more easily extracted. Once miners got past the upper ore deposits, they found that the lower ores contained large amounts of complex sulfides. As a result, a precipitous drop in the recovery rate of gold occurred. Failed attempts at introducing alternative methods of extracting gold contributed to the tensions and financial turmoil of the West, until Hill popularized the method of smelting.
Accordingly, he spent a portion of 1865 and 1866 in Swansea, Wales and Freiberg, Saxony studying metallurgy, and returned to the United States with a perfected method of smelting. Hill learned while abroad, especially in the coal mines, that the best method was that of copper matte. In this method - known as the Swansea process - copper sulfide ore was mixed with gold and silver ore and the copper acted as a vehicle to hold the gold and silver. After returning, he took up a permanent residence in Black Hawk, Colorado. While in Blackhawk, he had the opportunity to work with James E. Lyon, an entrepreneur who he had met on his first trip to Colorado, and who had erected the first real smelter there. However, his findings surpassed those of Lyon. He capitalized on the experience and with his professional training as a chemist and the knowledge gained in Europe, founded the Boston & Colorado Smelting Company, which encompassed numerous ventures aside from mining. Through the funding of numerous capitalists, Hill worked alongside popular metallurgists to oversee the smelting process and thus rose in wealth and popularity.
