Millions of years ago intense heat and pressure caused loose particles of carbon hundreds of miles below sea level to crystallize into diamonds. Volcanic eruptions then pushed the diamond-bearing ore close to the earth's surface
The ore, known as kimberlite, is dug or blasted from mines; the deposits are then crushed and boiled in grease and water to separate the diamonds. About 80% of the world's rough stones come from Angola, Australia, Botswana, Namibia, Russia, South Africa and Zaire
The rough diamonds are sorted and...