Synonymous with Conflict Diamonds. Diamonds that have been mined and sold to fund (often bloody) rebellions in mainly African countries, usually under inhumane conditions. This is an issue addressed by the Kimberley Process, an international agreement to ban the sale of such goods through normal channels. Kimberley has been successful to a large degree in curtailing the free flow of such stones, but has also made it possible for dealers to know their sources and refuse to buy goods and pass them along when they choose. Most choose to pass them by.
See the FAQ: How can I avoid conflict diamonds?