The diamond trade is an interesting study in commodity dynamics. Until very recently, there were effectively commodity markets in diamonds although they effectively divided them into categories that reflected origins, e.g. an alluvial diamond and a mined diamond and artificial diamond were not equivalents, and diamond colour was often a good guide to its origins.
Also, in the 1990s, the conflict diamond issue rose and made it important to distinguish diamonds by the route by which they reached the market - the whole service cycle of extraction rights, mining practices and the smuggling from or through conflict areas like Sierra Leone and Congo were becoming issues in diamond pricing and legitimacy of sourcing.
The Kimberly Process was the first comprehensive protocol for certifying diamonds as having been legitimately and legally mined and moved. It is now widely accepted, nearly universal. It is probably the best example, better even than the Cocoa Protocol, of a comprehensive outcome model that informs the commodity markets, and is intended to keep offensive products out of those markets entirely. Fair trade and safe trade measures are typically attempting, like these two industry-specific certifications, to guarantee that some institutional buying criteria are met by every unit of the so-called commodity.