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.
Many people believe that diamonds are formed from the metamorphism of coal. That idea continues to be the how diamonds form story in many science classrooms. Coal has rarely played a role in the formation of diamonds. In fact, most diamonds that have been dated are much older than Earth's first land plants - the source material of coal!