Turquoise semiprecious gemstone index and mineral information

Turquoise’s name derives from the old French word pierre tourques, meaning “Turkish stone” because it was believed that the Persian (Iranian) stone was imported to Europe via Turkey. Turquoise forms as a porous blue cryptocrystalline aggregate and is found as encrustations, nodules, or botryoidal masses, or in veins within rocks in arid regions. Pure blue color is rare; mostly turquoise is intermixed with brown, dark gray, or black veins of other minerals or the host rock. These stones are called turquoise matrix. The blue color is due to copper and/or iron.

Turquoise is opaque to semi-translucent and has a waxy to dull luster and takes a good polish. Because its porosity, it can fade or crack over time. The best quality turquoise is the sky-blue turquoise from Iran, near Nishapur. In Tibet the green turquoise is more highly prized.
Turquoise can also be intergrown with malachite. Because of its porosity, turquoise is often soaked with artificial resin, which improves color and at the same time hardens the surface.

Turquoise is regarded by the Iranians as jade is by the Chinese. The Iranian turquoise source was the mines of Neyshabur, in the Khorasan region of Iran. Iranians used turquoise to embellish thrones, sword hilts, horse trappings, daggers, bowls, cups and ornamental objects of all kinds. Before World War II turquoise was Iran’s principal export. Turquoise was believed to be a lucky stone, protecting the wearer from evil, and a cure for many ailments. American Indians and ancient Inca and Aztec cultures also venerated the stone.

Since turquoise is and expensive stone, there are many imitations on the market as well as treatments designed to improve its appearance. Glass imitations have existed since the Victorian times. Enamel was also used to imitate turquoise; the luster of enamel is greater than that of the natural stone. Other stones and materials have been used also; such as howlite, fossil bone odontolite, limestone and chalcedony; they are dyed or stained, and sold as natural turquoise. In 1972 the French manufacturer Gilson produced imitation turquoise, even including matrix in the imitation stones to give them the popular spiderweb pattern. There is also enhanced, coated, stabilized and reconstructed turquoise.

Reconstructed or pressed turquoise is turquoise powder and small chips bonded with liquid plastic resin, dyed and then baked. It is much cheaper than natural turquoise. Stabilized and coated turquoise involves soaking the rough material in an artificial resin or impregnating it with wax, to improve its color, to harden its surface for cutting or to maintain its appearance and strength over time. Enhanced turquoise is obtained by dyeing or staining the turquoise to improve the color. Oil, paraffin and copper salt also improve color and luster, but their results tend to be temporary. Turquoise can be found in Persia, Afghanistan, Australia, Brazil, Chile, China, Mexico, Russia, Tanzania, and Turkestan; in the United States in the Mohave Desert, Colorado, which has quality compact turquoise of a good color, Nevada and Arizona.

Turquoise is the last of the twelve gemstones of the ceremonial breastplate worn by the high priest Aaron, representing the twelve tribes of Israel as described in the Old Testament book of Exodus, and is also known as the month of December’s birthstone meaning, prosperity.

Mohs’ hardness: 5 – 6