“The critical factor in determining a favored new gemstone is not color, as many people might suspect. Rather, it is quantity. In other words, is the gem available in volumes substantial enough to support a commercial trade?
Unlike diamonds, colored stones do not conform to a universally accepted grading standard. To determine the value of a fine gem specimen, you need to know more than its 4Cs (color, clarity, cut and carat weight). You need to know its origin.
Until the Mozambique sapphire find, the bulk of the world’s fine blue sapphire came from Myanmar, Sri Lanka and the most illustrious source of all, the Himalayan territory of Kashmir. Kashmir sapphires can command as much as $25,000 per carat at wholesale, while look-alike stones from Madagascar may fetch only a third of that. But the market’s obsession with origin does not end there.
Prices on emeralds, for example, can vary by thousands of dollars, depending on whether the gems are from Colombia, Zambia or the less desirable tracts of Brazil. Much of that disparity comes down to aesthetics; the best Colombian crystals are prized for their electric green coloring, a product of near perfect combinations of chromium and vanadium. Do not, however, overlook the role that the Moguls of India played in building a centuries-old reputation for emeralds from Colombia’s famous Muzo district.”
Excerpts from an article by VICTORIA GOMELSKY, MARCH 16, 2014 (The New York Times)
The article encouraged me to read a bit more, so I checked the famous GemGuide site, and found this:
The term gemstone is applied to any of the one hundred or so naturally occurring minerals (diamond, ruby, sapphire, etc.) and organic materials (amber, pearls, ivory, coral, etc.) that are used for personal adornment or display. However, most of the popular gem materials encountered today are inorganic. The first use of a mineral or organic substance for personal adornment remains the subject of debate. But it is generally accepted that their use dates back at least ten thousand years.
To be classified as a gemstone, an organic or inorganic material must possess beauty, rarity, and durability. A gem’s beauty comes from its brilliance, fire, luster and color. In their rough form these attributes are often masked. Only after cutting and faceting and often other enhancements, can the true beauty be revealed. Durability refers to a combination of the material’s hardness (ability to withstand scratching), toughness (ability to resist breakage), and stability (ability to withstand chemical or physical change resulting from heat, light or chemical exposure).