Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form of carbon, but diamond converts to it extremely slowly.
Diamonds were used to engrave gemstones in India by 300 BCE. Diamonds can be burned. To burn a diamond, it must be heated to between 1290-1650 degrees Fahrenheit. House fires and jewelers’ torches can sometimes reach that temperature.
Diamonds were formed billions of years ago through a combination of tremendous pressure and temperatures of 1652–2372 degrees Fahrenheit at depths between 90 and 120 miles beneath Earth’s surface. Even though the U.S. produces almost no diamonds for commercial consumption, America buys more than 40 percent of the world’s gem quality diamonds – making it the world’s largest diamond market.