When you think of a diamond, the image that comes to mind is probably that of a clear, shining stone. Not all diamonds fit into this stereotype, however. Diamonds can be transparent, colored, opaque, or even mere dust. The value of a diamond is determined not only by its size and clarity, but also by which of these categories it falls into.
Diamonds are formed by intense heat and pressure exerted on carbon atoms far beneath the Earth's surface. Over time, the carbon atoms bind into a cubic structure and begin to crystallize. The crystallized carbon grows slowly over time into a diamond. Diamonds were carried to the surface of the Earth thousands of years ago by short, intense volcanic bursts. Diamonds are the hardest natural substance known to man and are widely valued for their beauty and durability.
Transparent diamonds form when no impurities are present in the surrounding material during the formation period. Transparent diamonds are very refractive. Light entering the diamond is slowed down and "trapped" -- thus creating the intense sparkle transparent diamonds are known for. This variety of diamond is more popular than any other, and is currently the standard choice for the modern engagement ring. While transparent diamonds are more expensive than any other precious stone, they are considerably less expensive than their colored counterparts.
Although a diamond's density prohibits the vast majority of impurities from entering the stone, some elements are capable of infiltrating a diamond's solid structure and altering its electron states. Altered electron states create the appearance of color in an otherwise colorless substance. Yellow diamonds contain trace amounts of nitrogen; blue diamonds contain boron and green diamonds result from extended exposure to radiation. Pink and red diamonds, however, result from structural changes to the stone caused by extreme pressure. Colored diamonds are the most rare and expensive variety of diamond in the world.
Opaque diamonds are neither transparent nor colored. They can range in hue from translucent and cloudy to solid black. The market for opaque diamonds is limited, as not all are considered to be gem-quality stones. For those that are gem-quality, many are made into jewelry or color-enhanced so as to be more aesthetically pleasing. The majority of opaque diamonds, however, end up being used in heavy industry to enhance saw blades, drill bits and engraving tools. The majority of diamonds mined in the world are opaque and are purchased solely for industrial uses.
Diamond dust is composed of tiny diamond crystals. These crystals are gem-quality, but too small to be used in the production of jewelry. Diamond particles can be mined, but are more frequently gathered as a by-product of diamond cutting. Diamond dust is relatively inexpensive when compared to other diamond varieties. Because of the lower cost, these particles are commonly used in the fashion and beauty industry as additives to makeup and nail polish. Diamond dust is also used to create high-quality nail files that do not dull over time.