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Carat Weight
A carat is the standard unit of measure used to describe the weight of diamonds and other gemstones. One carat equals 1/5 (.200) of a gram (or 200 milligrams). The word “carat” originated from the carob tree, whose tiny seeds are known for their uniformity and consistent weight. Before a standard measure was established, diamonds and gemstones were actually weighed against carob seeds. In 1913, the carat was adopted in the United States as the standard metric for measuring the weight of diamonds and other gemstones. The weight of smaller diamonds is usually expressed in points, where one point equals 0.01 carats (For example, 50 points is equivalent to 0.50 carat).

In most cases, the higher the carat weight, the greater the per-carat price of the diamond.  This is because the rarity of a diamond greatly increases with size. For example, the rarity of a 1.00 carat diamond is much more than twice that of a 0.50 carat diamond because it is statistically much more difficult to mine a 1.00 carat diamond than it is to mine a 0.50 carat diamond. In addition, a one carat diamond is much more valuable than a grouping of smaller diamonds that add up to one carat. Therefore, something labeled “1 ct TW” (one carat total weight) will be very different in price than something labeled “1 ct” (the weight of an individual stone).