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Gemstone Size

Just as with diamonds, a colored gemstone’s weight is measured in what is known as a “carat“, which is a small unit of measurement equal to 200 milligrams. However, a carat measurement is not very useful to purchasers of colored gemstones, since some gemstones are denser than others, and thus the weight of the stone does not give a good idea of its actual size. For example, the International Gem Society has noted that a diamond, sapphire, and opal, all of the same size and cut in the same round proportions, would each reach that same size at a different carat weight: a 6.5 mm round-cut diamond (with a specific gravity of 3.52) will weigh 1 carat; a 6.5 mm round- cut sapphire (specific gravity 4) will weigh 1.14 carats; a 6.5 mm round-cut opal (specific gravity 2.15) will only weigh .61 carats. Thus, it is best to have the dimensions of your colored gemstone to get an idea of its actual size. At Diamond Select, we offer area measurements for each gemstone: for round-cut stones, we provide the diameter, and for other shapes, we provide the length and width of the gem, in combinations that let you know the size of the stone. The dimensions provide an area in terms of millimeters (“mm”). You also can look directly at a picture of all colored gemstone jewelry we offer for sale, and can see the size of the stone relative to the setting.