Diamonds are made of the same substance that the lead in your pencil and coal is made of, pure carbon (graphite). Diamonds are the clearest and hardest mineral known on Earth. Natural diamonds are made very deep in the Earth’s mantle, about 150 km below the surface where high temperatures and pressure exist naturally Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years. Historically, the quality and size of diamonds have been limited to that available from nature. However, researchers can now synthesize various types of diamond in the laboratory that are harder, tougher and larger than those available natural diamonds.

Synthetic diamonds are manufactured in mass quantities for industrial use in a laboratory, produced synthetically in a high-pressure high-temperature process which approximately simulates the conditions in the Earth’s mantle.

In 2003, Japanese scientists successfully manufactured, on the basis of graphite, the world’s hardest synthetic polycrystalline diamonds. The team led by geologist Tetsuo Irifune of Ehime University had heated graphite to a temperature of 2,500 C� and applied the pressure of more than 3,000 tons using large-volume multianvil high-pressure apparatus. Through this process, they obtained nano-polycrystalline diamonds, which have peculiar nano-textures with exceptional hardness and toughness. The ultra-hard and ultra-heat resistant polycrystalline diamonds are useful in industry, for processing hard objects, drilling rocks, cutting, grinding and polishing and laboratory use. The physical properties and features of these diamonds allow scientists to study materials at pressure-temperature conditions ranging from those at Earth’s surface to those at the very center of Earth.