Value of Gemstones

A gemstone is valued especially for its great beauty or perfection so appearance is almost the most significant attribute of gemstones. Characteristics that make a stone good-looking and desirable are colour, unusual optical phenomena within the stone, an attractive inclusion such as a fossil, infrequency, and also sometimes the form of the natural crystal. Diamond is valued highly as a gemstone since it is the hardest material known and is able to reflect light with fire and glitter when faceted. However, diamonds are far from rare with millions of carats mined each year.

Traditionally, common gemstones were confidential into precious stones (cardinal gems) and semi-precious stones. The former group was largely determined by a history of ecclesiastical, devotional and ceremonial use and rarity. Only five types of gemstones were considered precious: diamond, ruby, sapphire, emerald, and then amethyst. In current usage by gemologists, all gems are measured precious, although four of the five original "cardinal gems" are usually—but not always—the most precious.

Rare and unusual gemstones, normally meant to include those gemstones which occur so uncommonly in gem quality that they are barely known except to connoisseurs, include andalusite, axinite, cassiterite, clinohumite and also iolite.

Factors influencing the esteem in which gems are held are attractiveness, durability, rarity, style, and size.