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How Are Diamonds Formed in Nature?

Diamonds are native crystalline carbon and the hardest known material. Diamonds are nearly colorless. When transparent and free from flaws, they are highly valued as precious stones. They are also used in industries, especially as an abrasive. Natural diamonds form when carbonaceous compounds crystallize under exposure to high temperature and pressure deep within the Earth's surface.

  1. Natural Process of Formation

    • Diamonds began forming some 3.3 billion years ago. The conditions of diamond formation occur at great depths inside the Earth, more than 150 km below the surface in a region known as the mantle, which consists of volcanic magma.

    Conditions of Formation

    • Diamonds are crystallized from carbon. The carbon gets mixed with molten magma, which forms in conditions of high temperatures (approximately 1,000 degrees centigrade) and great pressure (about 50 kbars or 50,000 times the atmospheric pressure of the Earth's surface).

    Location

    • Although diamonds form deep within the Earth, they are mined from the Earth's surface. They could be found at thousands of miles away from where they were formed. Magma is expelled at a great speed through volcanic pipes known as "kimberlite pipes," carrying diamonds with the magma. The process may occur 1 to 3 billion years after the formation of diamonds in the Earth's mantle. So, diamonds may be found in mines, rivers, or sea beds, but their exact site of formation cannot be determined from their site of discovery.

    Color

    • The color of diamonds may depend on the surrounding trace minerals mixed inside during the time of formation. Most diamonds are yellowish in color, and absolutely colorless diamond are rarely found. Impurities such as boron may impart a bluish tinge to a diamond. Secondary deposits are thought to have formed after erosion from primary deposits in volcanic pipes.

    Synthetic Diamonds

    • Artificial or synthetic diamonds can be manufactured in laboratories through chemical or physical processes. A laser beam is applied to a glassy solid carbon material. Many synthetic diamonds are similar in appearance to real diamonds but lack the full range of properties of naturally formed diamonds.

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