A diamond is a crystal made up entirely of carbon atoms that are arranged in an isometric, or cubic, matrix. A cubic crystal arrangement is one in which the crystal essentially expands outward at the same rate in all directions during its initial growth; the ideal result, when the crystal forms without any interference, is a pure and perfectly formed octahedral shape.
Diamonds are made up of pure carbon atoms that exist deep in the ground, exposed to intense heat and pressure over billions of years. Over time, this pressure builds up and forces the diamonds and rocks up toward the surface in a volcanic-like explosion. The explosion creates a very deep, wide hole called a pipe into which most of the diamonds settle; these deposits of diamonds are known as primary deposits. Other diamonds are washed away by water or erosion, and often settle into the coastal waters of nearby bodies of water; these are alluvial deposits. These deposits occur in many places around the globe; however, the largest commercial deposits exist in Angola, Australia, Botswana, Namibia, South Africa, Russia and Zaire, which produce 80% of the worlds diamonds.
A newly mined rough diamond looks more like a piece of glass washed up on the beach than like the polished gems sold in jewelry stores. Bringing out their beauty requires the skill and art of a trained diamond cutter.
The Ideal Cut is a cut based on a specific set of proportions for a round brilliant diamond proposed by gem cutter Marcel Tolkowsky in 1919. While Tolkowskys original theories presented only one particular combination of proportions for creating the best balance of brilliance and dispersion, today the American Gemological Society recognizes any diamond falling within a narrow range of proportions and finish quality as being an Ideal Cut (also called an AGS 0? or AGS triple zero).
Finding the rough diamonds is only the first step. Once diamonds have been mined and processed out of the overburden (that is, the kimberlite rocks in which they are imbedded), the rough crystals are sorted and categorized according to their size, color, shape and other characteristics.