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.
The Kimberley diamonds were originally found in weathered kimberlite, which was colored yellow by limonite, and so was called yellow ground. Deeper workings encountered less altered rock, serpentinized kimberlite, which miners call blue ground. See also Mir Mine and Udachnaya pipe, both in the Sakha Republic, Siberia. The blue and yellow ground were both prolific producers of diamonds.