A carat (or karat) is a unit of measurement for gemstones and is one of several factors that determine the value of a garnet. Just as the four C’s--cut, clarity, carat and color--determine the price of a diamond, they apply to the cost of a garnet.
How Color Determines Price per Carat
Garnets come in almost any color, and different colors fetch different prices. In 2010, a red garnet costs $20 to $30 per carat; a bright orange garnet, known as mandarin garnet, costs over $100 per carat. Dark green garnets are known as Russian demantoid garnets cost over $400 per carat.
How Quality Determines Value
Industrial garnets are stones used as abrasives, because they are very hard. However, their quality is low and would not make attractive jewelry if cut. These stones are very, very cheap per carat.
How Cut Determines Cost
Just as with any stone, the quality of the cut affects the amount of “sparkle” that comes from a gemstone. A good cut can show off the clarity of a gemstone or even cleverly hide inclusions, which are internal flaws.