Carbon trade in both types of diamonds exists, the two markets act in dramatically different ways. Unlike precious metals such as gold or platinum, gem diamonds do not trade as a commodity: there is a substantial mark-up in the sale of diamonds, and there is not a very active market for resale of diamonds. Industrial diamonds are valued mostly for their hardness and heat conductivity, with the gemological qualities of clarity and color being mostly irrelevant. About 80% of mined diamonds (equal to about 100 million carats or 20 tonnes annually) are unsuitable for use as gemstones are relegated for industrial
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,