An isomorphous mineral with chalcosiderite. Generally cut as a cabochon gemstone but frequently faceted or engraved. Often has an attractive blue or sky-blue color of fine-quality. A matrix of turquoise with minute grains of turquoise speckled in it is called rock turquoise. Turquoise matrix, which includes inferior turquoise is known as new rock turquoise. A network of fine black-brown veins of metallic oxides usually limonite, which look like a mosaic at the surface of the turquoise is known as spiderweb turquoise or Persian spiderweb. Fine quality turquoise with permanent color is known as old rock turquoise.

The fine sky-blue variety of turquoise from the USA locally is known as robin’s egg blue. North American turquoise is more porous and therefore paler than the Persian stone. In Egypt, turquoise was first mined around 2000 BC, it was called majkaat. Duklij was an old name for turquoise used by the Apache Indians and Xihuacan indigenious in prehispanic Nahuatl. The stone is porous but takes a high polish. Turquoise fluoresces under LWUV light from greenish-yellow to light blue and inert under SWUV light or X-rays. Some pieces lose color if exposed to daylight but that is temporary and can be restored.

Dyed stones are detectable by scratching or by placing a drop of ammonia on the stone surface, which will turn the stone greenish. Sometimes particles of true turquoise are bonded together with a resin or synthetic plastic, which is called as reconstructed turquoise. Turquoise is reniform to botryoidal in form. Occasionally is mistakenly called as sacred turquoise, which is actually a light blue smithsonite. Imitations are made from sodalite, haüyne, lazulite, variscite, prosopite, and wardite. Soaked or dyed imitation stones are plaster of Paris, glass, howlite, chalcedony, magnesite, and odontolite of organic origin. Sometimes gibbsite is coated with plastic to imitate turquoise and pyrite is added as inclusions with an apparent dendritic matrix is known as coated gibbsite.

Found in Nishapur and Baghu (Iran), Australia, Arizona and Nevada (USA), Eilat (Israel), Tibet, Bahia (Brazil), Zacatecas (Mexico), China, and Sinai Peninsula (Egypt).

North American Turquoise
Turquoise from Stormy Mountain Mine and Fox Mine in Nevada, Kingman and Bisbee in Arizona, Santa Rita in New Mexico, and Leadville in Colorado, USA. American turquoise is more porous and therefore paler than Persian stone.

Classification of Iranian Turquoise
Turquoises from Nishabur are divided in three classes: (a) Angoshtari, a Farsi or Persian term meaning stone for finger ring which is a sky blue turquoise without dendrite (matrix). (b) Barkhaneh, a Farsi or Persian term meaningsandy stone (size) of intermediate quality, sky-blue dendritic turquoise, from Khorassan, in NE Iran, which is divided into four categories, mostly used for inlaying and incrusting jewelry, bazu band (armlets), trappings, water-pipe, etc. Another spelling is barchaneh, barkhan, or barchane. (c) arabi, a Farsi or Persian term for pale colored, patched, or dendritic turquoise. (d) shirbu or shirfam, a Farsi or Persian term meaning milky of whitish color. (e) chagaleh, a Farsi or Persian term meaning unripe, turquoise with white crust. (f) tofal (literarily topal) a Farsi or Persian term meaning metal or metallic, large, flat, slab-like pieces of turquoise used for setting in metal such as bracelets, bazu-bands, amulets, etc. (g) goleh-kasni, a Farsi or Persian term meaning dandelion, stones of greenish color mostly bought by Afghans.

Turquoise Classifications in Nishabur and Nayshabur, Iran
Turquoises from Nishabur are divided according to its different sources into different qualities by the mine owners as: (a) Abu-Eshaghi, have fine dark color with high brilliance and quasi pure. (b) Azhari, fine and dark color but not like Abu-Es-haghi. (c) Soleimani, blue but slightly milky. (d) Zarmuni, contain golden spots of pyrite with less brilliance. (e) Khaki, sky-blue colored. (f) Abdul-Madjidi, fine dark color but not pure and soft. (g) Andelibi, milky but less so than Soliemani. (h) Abrash, a Farsi term for mottled or stone with two colors. (i) Sadja, a jeweler term for turquoise smeared with butter, it becomes darker but the color is only temporary, also called Massiha and mescha. (j) Tarmalah (literarily means impure or despised, may be derived from Damalah for cabochon), turquoises furrowed by other stones which are used as decoration. Besides the classification of turquoise mentioned above there are other two degrees relating to their age: (I) Old rock by where the color and luster do not change. (II) New rock where the color and luster change quickly.

The Mines of Nishabur, Iran
Turquoise mined in Nishabur from several shafts, galleries, and cavities with names: Abdulrazzaghi (or Abu Es-haghi the oldest mine), Maleki, upper and lower Zaki, Mirza Ahmadi, Abdul Karim, etc. Manutchehr-Danai (1977). Turquoise is mined in two kinds: (a) mining through shafts and galleries in underground in the solid rock, (b) the Khaki mines that mean digging in the detritus of rock washed down toward the bottom of valley. The ancient name of this deposit is Pashan.

Turquite
A commercial term for imitation turquoise made of reconstructed pieces of turquoise.

Bonded Turquoise
Particles of true turquoise are bonded together with a resin or synthetic plastic, which is named as reconstructed turquoise. ® Turquoise, imitation turquoise.

Turquesa
Is the Spanish term for turquoise.

Turqueza
Is Portuguese for turquoise.

Turquois
Another spelling for turquoise.