Nathaniel Peter Hill built the first successful smelter in the Rocky Mountains at Black Hawk, Colorado, in 1867. He introduced European smelting methods to the Rocky Mountains and revived a Colorado mining industry that had nearly exhausted the placer and free-milling gold and silver ores worked in the region since the Colorado Gold Rush of 1859.
Nathaniel Hill, a young chemistry professor at Brown University in Providence, Rhode Island, first visited Colorado in 1864. That year, he examined mining properties in Central City, took options on several, returned to Rhode Island, sold all but two of the options, and resigned his position at Brown. In February 1865, Hill returned to Central City to open mines on his two optioned properties. He installed a stamp mill and had some early success, but by the summer of 1865 the free-milling ores on the properties were exhausted. Below lay many tons of sulfides—complex copper and iron pyrites with important gold and silver values.
No successful smelter for sulfidic gold and silver ores had been built in the Rocky Mountains. Nathaniel Hill drew up a list of several possible smelting technologies, discarded one after another, and by November 1865 was convinced that the Welsh Swansea Process held the greatest potential. He went to Wales to observe the process, returned to Colorado to purchase 70 tons of Central City ore for shipment to Swansea, and sailed again to Swansea in the fall of 1866 to observe the test. It was successful. With these results in hand, Nathaniel Hill and four other investors organized the Boston and Colorado Smelting Company, naming Hill as General Manager. Black Hawk was selected as the smelter site. There were still no railroads in Colorado. The smelter had to be near the mines to keep shipping costs down.
Nathaniel Hill started up his Black Hawk smelter in January 1868, signed ore purchase contracts with Gilpin County mines, and in June shipped a 50%-copper matte averaging 50 oz. of gold and 100-200 oz. of silver per ton to Swansea for refining. Success followed success. Capacity was rapidly expanded at Black Hawk, and in 1872 a second smelter was built at Alma, Colorado.
Nathaniel Hill’s Swansea refining contract expired in 1873. Expanded production at Black Hawk and new production at Alma now made refining in Colorado economically viable. Hill hired Richard Pearce, a Cornishman, to develop a refining process and supervise the plant. Pearce’s process proved to be the best separation technique for gold and copper until electrolytic refining was introduced near the end of the century. To expand further capacity, Nathaniel Hill built a new smelter at Argo, near Denver, and started it up in 1879. The Black Hawk and Alma smelters were closed. The Argo smelter processed ores from throughout the western United States and northern Mexico and remained in production for 30 years.
From 1879 to 1885, Nathaniel P. Hill was a Senator from Colorado in the U.S. Senate. In his later years, he taught courses at the Colorado School of Mines. Nathaniel P. Hill Hall, dedicated in 1963, houses the Department of Metallurgical Engineering at the Colorado School of Mines.