The earliest diamonds were found in India in the 4th century BC, although the youngest of these deposits were formed 900 million years ago. A majority of these early stones were transported along with the network of trade routes that connected India and China, commonly known as the Silk Road. At the time of their discovery, diamonds were valued because of their strength and brilliance, and for their ability to refract light and engrave metal. Diamonds were worn as adornments, used as cutting tools, served as a talisman to ward off evil, and were believed to provide protection in battle. In the Dark Ages, diamonds were also used as medical aid and were thought to cure illness and heal wounds when ingested.
Surprisingly, diamonds share some common characteristics with coal. Both are composed of the most common substance on earth: carbon. What makes diamonds different from coal is the way the carbon atoms are arranged and how the carbon is formed. Diamonds are created when carbon is subjected to the extremely high pressures and temperatures found at the earth's lithosphere, which lies approximately 90-240 miles below the earth's surface.
Until the 18th century, India was thought to be the only source of diamonds. When the Indian diamond mines were depleted, the quest for alternate sources began. Although a small deposit was found in Brazil in 1725, the supply was not enough to meet world demands.
In 1866, 15-year-old Erasmus Jacobs was exploring the banks of the Orange River when he came across what he thought was an ordinary pebble but turned out to be a 21.25-carat diamond. In 1871, a colossal 83.50-carat deposit was unearthed on a shallow hill called Colesberg Kopje. These findings sparked a rush of thousands of diamond prospectors to the region and led to the opening of the first large-scale mining operation which came to be known as the Kimberly Mine. This newly discovered diamond source increased the world's diamond supply substantially, resulting in a significant decrease in its value. The elite no longer considered the diamond a rarity and began to replace this "common" stone with colored gemstones. Emeralds, rubies, and sapphires became more popular choices for engagement ring stones among the upper class.
In 1880, Englishman Cecil John Rhodes formed De Beers Consolidated Mines, Ltd in an effort to control the diamond supply. Although DeBeers was successful in their efforts to control the supply of diamonds, demand for the stone was weak. By 1919, diamonds were devalued by nearly 50%.