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.
Placer Diamonds in the Northwest Territories. Diamond Mining in the U.S.A. Space Diamonds / Carbonado. For whatever reason, very few miners are looking for diamonds in the U.S. That is a real shame, because the U.S.A. sits on an extremely old massive Craton. Cratons are the earth's diamond making factories, 150-250 miles down.