Diamonds were born in dying volcanoes. As the molten lava in the necks of these volcanoes became solid, the tremendous heat and pressure acted on the carbon that was present in the lava. The heat and pressure forced the carbon atoms to line up in eight sided crystals. It is this shape that gives diamonds their special qualities. Not all volcanoes contained carbon in their lava. For this reason diamonds were formed in only a few volcanic regions.

The hardened lava plugs in the necks of the dead volcanoes are called pipes. As the centuries passed, the rock in the upper portions of the pipes broke down, forming soil. Some of the diamonds were washed into streams and valleys below the volcanoes. In some parts of the world, erosion wore the old volcanic pipes completely away.

Historians believe that the earliest diamonds came from India. Several diamond deposits were known and worked in ancient times in the region of Hyderabad in central India. These diamonds were bought and sold by traders in the city of Golconda. The name Golconda later came to be used to mean any rich mine.

In the 1720s, large diamond deposits were found in Brazil by miners looking for gold in the Jequitinhonha River. More than a century later, in 1867, children playing along the banks of the Orange River at Hopetown found the first South African diamond. The stone weighed about 22 carats. In 1869, a stone almost four times larger was uncovered in a stream east of Hopetown. This led to a diamond rush in South Africa and the discovery of the famous Kimberley fields.

Today most of the world's diamonds come from South Africa. Many other countries also contain deposits, and new fields are constantly being discovered. Huge diamond fields were found in Siberia in 1956. There even are diamonds in the sea. Dredges that work like vacuum sweepers suck the diamond bearing gravel from the ocean floor off the southwest coast of Africa.

Diamonds are mined by digging out weathered lava soil from volcanoes. They also are recovered from gravel deposits in streambeds. Many mines close down after the soft layer at the top of the volcanoes has been removed. Mining diamonds deep in the pipes is often too expensive for the small amount that can be recovered. Only pipes that are especially rich in diamonds are deeply mined.

Blasted rock and earth that contain diamonds are full of gravel as well as diamonds. The mined material is crushed and then mixed with water. The mixture is rocked back and forth on a sloping steel table that is thickly covered with grease. As the table rocks, the gravel slides down the slope and off the end and the diamonds stick to the grease. Skilled sorters can then pick out the diamonds.