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
Commodity (Marxism) of socially necessary labor have the same exchange value. By contrast, prices are normally measured in money-units. For practical purposes, prices are, however, usually preferable to labour-hours, as units of account, although in capitalist work processes the two are related to each other (see labor power). The seven basic forms of commodity trade can be summarised as follows: The hyphens ("-") here refer to a transaction applying to an exchange involving goods or money; the dots in the last-mentioned circuit ("...") indicate that a value-forming process ("P") occurs "in between" purchase of commodities and the sales of different commodities. Thus,