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.
Let's say you want to find some malachite specimens to add to your gem collection. This mineral is often found near limestone and copper deposits and, within the United States, is most often found in Arizona [source: Cook and Kirk). Or maybe you're looking for the big score and want to find a diamond. Because diamonds are created under extreme pressure, they form deep within the Earth. They're most common in areas where deep mantle rocks have been pushed to the surface by geological processes.