Such gems are called "blood diamonds" or "conflict diamonds."
With the opening of a movie on the topic, and as commercials urge holiday shoppers to buy diamonds for their loved ones, speaking about the unpleasant seems necessary.
Blood Diamond stars Leonardo DiCaprio as a smuggler in the West African nation of Sierra Leone during the civil war of the 1990s. It does a good job of portraying the high human cost of conflict.
The movie shows rebels capturing civilians and making them mine for diamonds. The gems then are traded for weapons.
As happens in real life, the movie's main child character is snatched from his family, trained to wear a soldier's uniform and to thoughtlessly commit unthinkable atrocities.
That has happened during wars in Angola, Sierra Leone, Liberia and the Democratic Republic of Congo.
Previous publicity surrounding blood diamonds led the diamond industry, as well as diamond-producing and diamond-buying nations, to launch the Kimberly Process in 2003 to certify that diamonds in jewelry stores do not perpetuate conflict. The process involves checking the origin of gems and their previous stops from rough diamond to polished, cut jewelry. Vigilance, transparency and enforcement by nations and the diamond industry are essential.
Kimberly has made a big difference. But many conflict diamonds still are set on gold bands or dangle from earrings.
In 2005, U.S. consumers bought $33.7 billion in diamond jewelry. Numbers like that make the United States the world's largest consumer of diamond jewelry - and gives Americans power to clamp down even further on this illicit trade.
Americans can urge their federal officials to follow the recommendations in a September report by the U.S. General Accountability Office. It called on U.S. Customs and Border Protection agents to do a better job of checking the documentation of diamonds.
The ultimate power rests with consumers. Ask your jeweler if the diamond you are interested in purchasing is certified not to have come from a conflict zone. Walk out if he cannot provide that certification.
With blessings comes responsibility. Many Americans have the means every month of the year to indulge their diamond dreams. But with a little extra effort they can help children caught in conflict.