Turquoise, the blue cousin to lapis lazuli, has been known and valued for thousands of years. The early mines in Sinai, Egypt, were already worked out in 2000 B.C. Today the best quality Turquoise is found in Iran. Turquoise was first sent to Europe through Turkey, hence its name, which means “Turkish” in French.
The brilliant sky-blue color has made Turquoise a classic gemstone, especially when set in silver. Cut en cabochon Turquoise stones are used for all kinds of jewelry: brooches, necklaces, bracelets, rings and earrings. Due to its relative softness, 5-6 (Mohs scale) it can be carved into ornamental objects but requires some care. Light, perspiration, oil, cosmetics and household chemicals can all affect the color of Turquoise.
Turquoise has long been appreciated as a holy stone, a good-luck-charm or a talisman. It is believed to promote good fortune, happiness, and long life.
Turquoise is a birthstone for those born in December.
Turquoise comes in sky-blue, blue-green and apple-green. Sky-blue is the most popular color, though green is the rarest. Pure blue colored Turquoise is rare. The gems are mostly mixed together with brown, dark gray, or black veins of other minerals or of the hosting rock (like chalcedony or opal, brown limonite, black chert, or white kaolinite). Those stones are called Turquoise matrix. Color ranges through shades of blue to blue-green, to yellowish green depending on the amount of copper (reponsible for blue) chromium or vanadium (reponsible for green,), and iron (reponsible for yellow). There are rare specimens of blue-violet color, which contain strontium impurities.
In general the color is only stable if the stone is not exposed to strong light, high temperatures, perspiration, oil, cosmetics and household chemicals. A loss of its natural water content (18-20%) results in undesirable color-changes as well. The most desired sky-blue color changes at 250 degrees C (482 degrees F) into a dull green. Most of the Turquoise found in the United States contains Fe, substituting Al, which causes a greenish color.
Turquoise is an affordable stone for its carat weight. It’s fairly soft, 5-6 on the Mohs scale, and requires some care. A Turquoise ring should always be removed before hands are washed.
A spotless sky-blue is the most desired color of turquoise, but rarely found. Apple green turquoise is rare.