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Article: Turquoise


Names and Properties of Turquoise

  • The word 'turquoise' dates back to the 17th century and is derived from the Old French 'turquois' meaning Turkish.
  • The gemstone was first brought to Europe from Turkestan or another Turkic territory.
  • Pliny the Elder referred to the mineral as 'callais' and the Aztecs knew it as 'chalchihuitl.'
  • Turquoise is also known as 'fayrūzeh' in Modern Persian.
  • The Persian turquoise mined near Nishapur, Iran, is used as a reference for evaluating turquoise quality.
  • Turquoise has a maximum Mohs hardness of just under 6.
  • It is a cryptocrystalline mineral and rarely forms single crystals.
  • The color of turquoise ranges from white to powder blue to sky blue, and from blue-green to yellowish green.
  • Turquoise has a waxy to subvitreous lustre and is typically opaque.
  • Its refractive index varies from 1.61 to 1.65 with birefringence of 0.040.

Formation and Occurrence of Turquoise

  • Turquoise deposits begin with hydrothermal deposition of copper sulfides.
  • Copper is leached from a host rock and redeposited in a more concentrated form as a copper porphyry.
  • Turquoise forms when meteoric water percolates through the copper porphyry, oxidizing the copper sulfides.
  • The acidic, copper-laden solution reacts with aluminum and potassium minerals to precipitate turquoise.
  • Turquoise deposition usually takes place at a relatively low temperature in arid environments.
  • Turquoise was among the first gems to be mined and many historic sites have been depleted.
  • Small-scale operations, often seasonal, are still worked by hand in remote deposits.
  • Turquoise is sometimes recovered as a byproduct of large-scale copper mining operations.
  • Deposits typically take the form of small veins in partially decomposed volcanic rock in arid climates.
  • Iran has been an important source of turquoise for at least 2,000 years.

Uses and Cultural Associations of Turquoise

  • Turquoise has been prized as a gemstone for millennia due to its rare and valuable blue-to-green hue.
  • It has been used to cover the domes of palaces in Iranian architecture.
  • Turquoise is used in jewelry, carvings, and decorative objects.
  • The introduction of treatments, imitations, and synthetics has devalued turquoise in the market.
  • Turquoise may be peppered with flecks of pyrite or interspersed with limonite veining.
  • Turquoise has been used by the Egyptians since at least the First Dynasty in ancient Egypt.
  • Turquoise is the traditional birthstone for those born in December and is considered sacred to the Zuni and Pueblo peoples.
  • Turquoise has been esteemed as a holy stone, bringer of good fortune, or talisman in many cultures.
  • Ancient Egyptians used turquoise in grave furnishings, dating back to approximately 3000 BCE.
  • The goddess Hathor, associated with turquoise, was the patroness of the Serabit el-Khadim mine.

Turquoise Sources in Different Regions

  • The Southwest United States, including Arizona, California, Colorado, New Mexico, and Nevada, is a significant source of turquoise.
  • Pre-Columbian Native Americans mined turquoise in California and New Mexico.
  • Cerrillos, New Mexico is believed to be the location of the oldest turquoise mines.
  • Arizona is currently the most important producer of turquoise by value.
  • Nevada has over 120 mines that have yielded significant quantities of turquoise.
  • Turquoise artifacts have been found in the Eastern Rhodopes in Bulgaria since the fifth millennium BCE.
  • China has been a minor source of turquoise for over 3,000 years.
  • The Lynch Station in Campbell County, Virginia was the first deposit of distinct, single-crystal turquoise discovered in 1912.

Types of Turquoise and Detecting Fake Turquoise

  • Viennese turquoise, made from precipitated aluminium phosphate coloured by copper oleate.
  • Neolith, a mixture of bayerite and copper(II) phosphate.
  • Gilson turquoise, a simulant that closely resembles true synthetic turquoise.
  • Dyed howlite and magnesite, common imitations of turquoise.
  • Other natural materials occasionally confused with or used in lieu of turquoise, such as variscite, faustite, and chrysocolla.
  • Gemologists use non-destructive tests to detect fakes.
  • Close examination of surface structure under magnification.
  • Natural turquoise has a pale blue background with flecks of whitish material.
  • Manufactured imitations have a uniform dark blue color and granular or sugary texture.
  • Glass and plastic imitations have greater translucency and visible bubbles or flow lines.
  • Historical treatments to enhance color and lustre, such as waxing and oiling.
  • Treated turquoise may develop a white surface film over time.
  • Oil and wax treatments can be restored with skill.
  • Finer turquoise is often glued to a base of stronger foreign material for reinforcement, known as backing.
  • Backing increases the durability of thinly cut turquoise.
  • Zachery Treatment, created by Jam.

Turquoise Data Sources

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Knowledge Graph

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