Diamonds have been known since antiquity. The Greeks named this gemstone 'adamas', meaning invincible, indestructible. The earliest recognized sources of diamonds were placer deposits east of the Deccan Highlands in India, in the region called Golconda. These deposits produced many large, famous, high-quality stones, including the fabulous blue "Hope Diamond". In the past 2000 years, these mines produced about 12 million carats of diamonds.
In 1725, placer deposits of diamonds were discovered in Brazil, and they quickly surpassed India's total production. In the first 150 years, they produced 16 million carats. The kimberlite pipes through which diamonds are delivered from beneath the Earth's crust to the surface were never identified. Indeed, some experts suggest that the diamonds found in Brazil actually weathered from kimberlite pipes in Africa prior to the breakup of the continents and the opening of the Atlantic Ocean roughly 150 million years ago.
The diamond production of India and Brazil was soon to be dwarfed, however. In December of 1865, Erasmus Jacobs, the 15-year-old son of a farmer found a pretty stone and took it to his home near Colesberg, South Africa. The stone was given to a friend of the family, Schalk Van Neikirk, who discovered it to be a 21-carat yellow diamond, named the "Eureka". It sold for £500, five times the cost of a comfortable house in England at the time.
The "Eureka" diamond did not attract worldwide attention, but in 1868, a young Griqua tribesman named Swartboy found a pretty stone near the Orange River and asked Van Neikirk if he would buy the stone. Van Neikirk immediately offered him every head of livestock on his farm: 500 sheep, 10 cows, and a horse. A huge price for a pebble found on the ground, yet Van Neikirk soon sold the 83.5 carat diamond (later named the Star of South Africa) for £11,200, and the world took notice. Within weeks, thousands of prospectors from around the world flocked to South Africa in search of diamonds and instant wealth. Within twenty years, South Africa was producing 3 million carats per year of diamonds.
While the initial finds were alluvial, tracing the source upriver led to the discovery of the first kimberlite pipes: the source of the diamonds. A single one of these, the Big Hole in Kimberly, South Africa (and for which the rock kimberlite is named), produced 14 million carats of diamonds in 42 years of production. Note that 25 million tons of kimberlite were excavated - barely a half-carat of diamond was found in an average ton of ore. Still, this qualifies as an exceptionally rich diamond ore.
* excerpt by Google