Most natural diamonds have ages between 1 billion and 3.5 billion years. Most were formed at depths of 150 to 250 kilometers (93 to 155 mi) in the Earth's mantle, although a few have come from as deep as 800 kilometers (500 mi). Under high pressure and temperature, carbon-containing fluids dissolved minerals and replaced them with diamonds. Much more recently (tens to hundreds of million years ago), they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites.
Diamonds have high optical dispersion, allowing the stone to disperse a spectrum of different colors. They are traditionally colorless or white. Because of the way Diamonds form from gases underground, it is rare for them not to be cloudy or have a tint of yellow or brown. Colorless diamonds are the cleanest and sparkle the most. However, there are other tints such as faint pink or yellow hue. A strong tinted diamond with an even tint and good clarity is even more rare.
South Africa is the highest exporter of diamonds followed by Australia, Thailand, China, Borneo, Russia, Brazil, Guyana and Venezuela.