Thermoplastics, in basic terms, are melt-processable plastics (materials that are processed with heat). When enough heat is added to bring the temperature of the plastic above its melt point, the plastic liquefies (softens enough to be processed).
In the U.S., diamonds have been found in Arkansas, Colorado, Wyoming, and Montana. In 2004, the discovery of a microscopic diamond in the U.S. led to the January 2008 bulk-sampling of kimberlite pipes in a remote part of Montana.
SLIDESHOW: 910-carat diamond found in southern African kingdom The largest diamond ever excavated is the Cullinan Diamond, a 3,106.75-carat gem found in Cullinan, South Africa, in 1905. The diamond, which is also known as as the Star of Africa I, was cut and used in the British monarchy's crown jewels. Letseng is the same mine where the 603-carat Lesotho Promise diamond was discovered in 2006, Elphick said.