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.
Diamonds are formed as an allotrope of the element carbon, at depths greater than 90 miles. The pressure and heat at this depth was critical to the formation of the diamonds that are mined at the surface today. At crustal pressures, the stable form of carbon is the allotrope graphite.