The fiery brilliance of the diamond has created it the planet's favorite jewel. The word comes from the Greek term adamas, which means “unconquerable.” The diamond is the hardest natural substance found on Earth. Diamond-tipped industrial tools will cut through granite as simply as a steel saw cuts through wood.

Diamonds are crystals of pure carbon that have been subjected to tremendous pressure and heat. This process is believed to have taken place deep within the Earth. Artificial, or man-made, diamonds became possible in 1955, when the General Electric Company used laboratory equipment to subject graphite to great pressure and heat.

The weights of each gem and industrial diamonds are expressed in metric carats. One carat equals one fifth of a gram. Diamonds were most likely fashioned various years ago in molten lava. Because the lava flowed to the Earth's surface through vents known as pipes, it cooled and solidified into kimberlite, a blue rock. Kimberlite contains the diamonds and is understood to diamond miners as blue ground.

Diamonds are found on all continents. India was once a chief source. In about AD 600 diamonds were found in Borneo and are still mined there. The rich fields of Brazil were discovered in the 1700s. In the nineteenth century even richer diamond fields were found in South Africa. Most of the globe's diamonds are mined in African countries. The Democratic Republic of the Congo (formerly Zaire) produces mostly industrial diamonds. South Africa is the foremost supply of gem-quality diamonds. Congo, Ghana, Namibia, and Angola are alternative major suppliers. Russia has diamond-mining operations in northeastern Siberia. Since the late Nineteen Seventies several diamonds are found in Australia.

About 80 p.c of the world's diamond output is employed for industrial purposes. The United States imports some two thirds of all diamonds mined. Some diamonds are found in Pike County, Ark., close to Murfreesboro, and diamonds have additionally been found within the Higher Peninsula of Michigan.

In mining kimberlite, shafts are sunk a long way from the blue-ground pipe. Tunnels are then driven from the mine shaft to the pipe. Elevators take the kimberlite aboveground, where it's processed. The shaft of the Kimberley mine in South Africa is more than three,500 feet (1,000 meters) deep. Pipe mines are found in South Africa and Tanzania. Arkansas diamonds are also taken via pipe.

In other parts of Africa and in the rest of the world, diamonds are found in alluvial soils, or soils of sediment that have been deposited by running water. In 1962, however, diamonds were for the primary time taken from the ocean floor, near Namibia. In this process a rubber hose twelve inches (thirty centimeters) in diameter is extended from a barge to the underside of the sea. Sort of a huge vacuum cleaner, it sucks up gravel. On the typical a large amount of gravel contains one diamond, whereas it needs some twenty tons of kimberlite to yield a diamond.