Internet users can find recent gemstone value charts on the International Gem Society website and Open Alias Corporation's gem evaluation website. Both websites show the value per carat of each gemstone in U.S. dollars, as of 2015.
Donald Clark founded the International Gem Society in 1998. The society has members on every continent except Antarctica. Website users must pay an annual fee to view gemstone values on the Gemstone Pricing Guide. Other member benefits include access to a gemology course, eNews and reference library.
A group of mathematicians and gemologists started Gemval in 2003, and Open Alias Corporation bought the business in 2005. Gemval offers free appraisals of natural gemstones and has a paid subscription service for the appraisal of more precious gemstones. The gemstone value chart shows prices for gemstones weighing in at one, three, five, 10 and 30 carats. Users can view the range of prices for specific gemstones based on weight and color variations.
The market value of gemstones is based on their weights. Gemstones are measured in carats, and a carat equals 200 milligrams. Rare gemstones bring higher prices per carat. Higher-priced gemstones have medium-toned color that is intense, vivid and pure, and they do not have any inclusions that affect the gemstone's brilliance. The cut should maximize the light that is returned to the viewer's eye.