Ah...we've finally rolled around to my birthstone, and my favorite gem, the diamond!

A diamond is simply carbon, just like charcoal or graphite. In a diamond, each carbon atom is bonded to four other carbon atoms in a tetrahedral structure, much like a pyramid. Each link or bond is the same length, and the tetrahedral formation is therefore completely regular. It this strength and regularity which makes the diamond very hard, non-volatile and resistant to chemical attack. A diamond is the hardest known naturally occurring substance.

A diamond is an ideal gemstone because it is extremely hard, and also very tough and hard-wearing, and this helps it to take a very high polish. In its pure form it is colorless, has a high refractive index, so has a very high lustre. It possesses high dispersion, meaning that different light wavelengths are diffracted differently, giving a strong scintillating play of prismatic colors.

Diamonds seem to have been known for about 3,000 years, being mentioned in Exodus chapter 28, however in early times, other hard minerals were often confused with diamond. It is thought that the earliest diamonds were found in about the 12th century B.C., in India , which remained the most important, if not the sole, source until 1725, when diamonds were discovered in Brazil. The Indian and Brazilian deposits had been almost exhausted when, in 1866, the Eureka diamond was discovered in South Africa, followed by the Star of South Africa in 1869. Shortly afterwards, the great South African diamond rush started, and South Africa remains one of the world's most important sources of diamonds today.

Diamonds have since been discovered in many other regions of the world, including Russia and Australia. Until the South Africa finds, diamonds were so rare and valuable, that they were only owned by the very wealthy.

Color
A pure diamond, if such a thing exists, is colorless. Most diamonds are slightly coloured, even if the coloring is almost imperceptible. The most common is yellow which is caused by tiny amounts of nitrogen being present in the crystal structure, while others are gray, light brown or greenish. Diamonds can be almost any color, although strongly colored attractive specimens are very rare. As with many gemstones, colors can be artificially produced or modified. Some fancy colored diamonds are produced by irradiation and subsequent heat treatment. Natural fancy colored diamonds command very high prices, especially the more more popular colors. Fancy colored diamonds where the color has been artificially produced are no less beautiful, but sell for more normal prices.

Clarity
It is well known that most diamonds contain slight imperfections or flaws. More than likely, there is no such thing as a perfect diamond. The higher the clarity grade of a diamond, the higher its desirability, and therefore its price.

Cut, Proportion, and Shape
Cut can have several different meanings. First, it can describe the shape and facetting pattern of the diamond, as in the modern round brilliant cut, the single or eight cut, pear shape, emerald cut, square, baguette, oval, heart, triangle, princess, marquise or fancy. Second, it can mean the accuracy of the facetting, and the proportions of the stone, and lastly it can apply to the polish or surface finish of the stone.

Carat
Carat weight is not a factor which denotes diamond quality. It purely denotes the size of a diamond, by its weight. Obviously it also affects the value or price of a diamond, because consumers tend to prefer bigger rather than smaller diamonds. Large diamonds are also rarer than small diamonds.