Precious Gemstones

The definition of the term "precious gemstone" isn't written in stone (pun intended). In the 1800s only diamonds, rubies, sapphires and emeralds were classified as precious gemstones. There was a time back in the dim and dusty past when amethyst was considered a precious gemstone, but large deposits of amethyst were discovered in Brazil in the 19th century, and the amethyst was demoted to "semi-precious gemstone" status.

Pearls have been classified as precious gemstones, but pearls aren't really stones at all. Opals have also been classified as precious gemstones in years gone by. At times in history aquamarine, peridot, and cat's eye were considered "precious stones" simply because they were in vogue and thus in demand.

Today gemstones aren't really classified as precious or semiprecious gemstones. In the gemstone trade, almost all gemstones are used to make jewelry. The value of the jewelry is determined not by the distinction of the stones set in the jewelry but rather by such factors as the brand name, the designer, fashion trends, supply, or any combination of those factors.

There is standardized grading only for diamonds. Diamonds are graded according to preset factors: carat weight, clarity, color and cut. But there is no set of standards in regard to other gemstones. There's only one laboratory (AGL) that grades colored gemstones and the gemstones are graded based on proprietary system that was developed by AGL. There is no universally accepted grading system for any stone except diamonds.

There are several methods used to enhance the appearance of colored gemstones; heat, radiation, waxing, oiling, and fracture filling. Depending on the type and extent, treatments can affect the value of the stone.

The monetary value of stones can be determined by a variety of factors, not the least of which is the history of the stone. Stones that have long and star-studded pasts increase in value with each passing year.