Gold costs were about $317 per troy ounce in 2007, but these can vary widely depending on mining type and ore quality; global mine production amounted to 2,471.1 tonnes. After initial production, gold is often subsequently refined industrially by the Wohlwill process which is based on electrolysis or by the Miller process, that is chlorination in the melt. The Wohlwill process results in higher purity, but is more complex and is only applied in small-scale installations. Other methods of assaying and purifying smaller amounts of gold include parting and inquartation as well as cupellation, or refining methods based on the dissolution
Standard & Poor's Commodity Index Standard & Poor's Commodity Index The Standard & Poor's Commodity Index (SPCI) is a commodity price index that measures the price changes in a cross section of agricultural and industrial commodities with actively traded U.S. futures contracts, stretching across five sectors - Energy, Metals, Grains, Livestock, and Fibers & Softs. Only commodities that are consumed for industrial use are included in the index. Weights in the index are determined by the dollar value of Commercial Open Interest (COI) for each component commodity, and rebalanced annually each February. Effective January 31, 2008 Standard & Poor's discontinued calculation and publication of the