Diamond

History
Diamonds have been known to man for many hundreds of years, first making their appearance in India around 400 BC. Because of their extreme resistance to scratches and wear, they were attributed with magical powers which could be bestowed upon the lucky wearer of such a stone. Such stones which had "magical" abilities were regarded as powerful talismans, and were jealously guarded. Diamond was regarded as conferring invincibility and fearlessness upon its owner. The word "diamond" comes from the Greek "adamas", meaning "to dominate". Diamonds were found in or near stream beds and alluvial flood plains, washed down from the mountains, and while finding a diamond of size was extremely rare, the gem gravels were routinely dug up, washed, and arduously sorted for the precious gems. Today mining companies look for kimberlite pipes and take core samples to search for possible diamond deposits. Likely sites are staked out, and successful mines operate anywhere from five to thirty years, depending on yield.

Features
The most common form of a diamond crystal is an octahedron, though flat tabular crystals are also common. Sometimes rough diamonds look like chunks of glass without any crystal shape. Triangular growth marks, called trigons, can sometimes be seen on crystal faces. A trigon always points in the opposite direction of the crystal's growth.

Treatments
The majority of diamonds on the market are white, and range in purity of colour from D to M, with M having a yellow, greyish or brownish tint, and clarity grades of F (flawless) to I3 (many or large inclusions, visible to the naked eye). In order to improve clarity, colour or both, diamonds can be subjected to a variety of treatments. Fracture filling cavities with a suitable compound can improve the apparent clarity of a diamond, however these fillings can be detected. Some fillings may leach out of the diamond if the stone is heated, as may happen during a repair, while other fillings may expand so rapidly that the stone may become further damaged. Laser drilling to reach black inclusions allows for bleach or acid to whiten the offending material, giving the image of a whiter stone. High pressure and high temperature can improve the colour of a diamond, though clarity frequently suffers, as "carbon spots" can result. Irradiation of diamonds can produce colours like pink, purple, blue, green, teal, red, deep cognac, neon yellow-green and yellow. While some of these colours do occur naturally, others (like the neon yellow-green) do not, and are sometimes the result of combined treatments. Other less common treatments include dyeing and painting.

Principal Deposits
Diamonds were originally found in India, Indonesia, and Borneo, as early as 400 BC. The diamond discoveries in Brazil occurred in the early 1700's, followed closely by several African nations, including South Africa, Rhodesia, Ghana and Sierra Leone. Major diamond discoveries have also occurred in Australia, Russia, and most recently in Canada's Northwest Territories and Quebec.

Rarity
A totally colorless, perfectly flawless diamond is extremely rare, and the greater the carat weight, the rarer it becomes. This is why a grading system to determine color and clarity has been established. Even two diamonds weighing the same, both with the same color and clarity grade, are different from each other. No two diamonds are exactly alike.