more about diamonds

Diamond is the ultimate gemstone in several ways:

Hardness: Diamond is a perfect "10", simply the hardest substance known by a wide margin. Nothing can scratch a diamond other than another diamond. And a diamond can scratch anything, even a sapphire.
Clarity: Pure diamond is completely colorless and transparent over a larger range of wavelengths (from the ultraviolet into the far infrared) than is any other solid or liquid substance - nothing else even comes close.
Thermal Conductivity: Diamond conducts heat better than anything - five times better than the second best element, Silver! This characteristic is the basis for "diamond tests", as it is simple and cannot be faked.
Refraction: Diamond has a relatively high index of refraction (ability to bend light), which gives it the high luster called adamantine.
Dispersion: Diamond has a relatively high optical dispersion which gives diamond the "fire" that makes it so desirable.
Diamonds may be nearly any color in the rainbow plus browns, grays, and white. Shades of yellow are most common, followed by colorless. Blue, black, reddish, and greenish are more valuable (some extremely so).

Diamonds are found in a type of rock called "Kimberlite", which comprises the core of certain volcanoes over especially thick portions of the earth's crust. This hard stone is mined and then crushed between giant steel rollers. The kimberlite is reduced to fine gravel, yet the extremely hard diamonds come out unharmed! Water is added and a grease covered roller sorts the diamonds from the gravel, as the diamonds stick to the grease. Typically, a single carat of diamond is recovered from a ton of rich ore.

Diamonds are found in many areas including South Africa, Russia, and even in Arkansas in the USA. In all cases, diamonds formed deep within the earth's mantle, and were brought to the surface in volcanic eruptions. In many cases, the diamonds weathered out of the kimberlite by natural processes, and were transported downstream by water. Many diamonds are mined in the resulting alluvial deposits in areas such as along the coast of South Africa.