In addition to the round brilliant, other popular cuts include emerald, marquis, pear, oval and square. The the size, or weight, of the diamond is measured in carats. One carat is divided into 100 points, so that a diamond of 75 points weighs .75 carats. The term Carat is derived from the ancient Carob Seed from the locust tree, used as a medium of exchange on early pan-balances. In the early 1900's the Metric Carat was established.
Diamonds come in a variety of colors, from yellow to brown, red to blue and so on.
These colored diamonds, know as fancies, are valued for their depth of color. Conversely, the more popular white diamonds are valued for their lack of color. The most highly valued, rarest and most costly diamonds are colorless. Colorless stones are graded D. Color grading continues down through the alphabet, with each letter designating a yellower tint. Inclusions can interfere with the passage of light through the stone, diminishing the sparkle and value of the diamond.