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).
Where diamonds are found in the United States - Wyoming. Diamond Kimberlite pipes have been found in Wyoming, near the Colorado-Wyoming state line area referred to as the Aultman, Ferris and Schaffer kimberlites. The Herkimer Diamond Mine and the Ace Of Diamonds Mine - New York.
The oldest and most famous diamond mine in North America is the Crater of Diamonds which is just south of Murfreesboro, Arkansas. Diamonds were first suspected in the area and in 1889, state geologist John Branner gave the area a thorough surface search and didn't find anything.