Turquoise

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Roman cameo
MFA# 99.109

Description

Navajo bracelet
MFA# 2004.2219

An opaque sky-blue semiprecious gemstone. Turquoise is composed of a hydrated basic copper aluminum phosphate mineral. It was used for beads as early as 5000 BE in Mesopotamia. Major deposits were worked in Iran (Nishapur, Juh-e Zar, Kuh-i-Firouzeh) and on the Sinai Peninsula. Turquoise is also found in Siberia, Turkestan, Germany (Saxony), France, England (Cornwall), Australia and the U.S.(Mexico, Arizona, Colorado, California, New Mexico). Turquoise can be blue, greenish blue or green with inclusions of red sandstone. Turquoise is used for cabochon jewelry, inlays, beads and small carvings.

Synonyms and Related Terms

Turquoise stone

turqoius; calliana; callais; Mecca stones; Türkis (Deut.); turquesa (Esp., Port.); turquoise (Fr.); turkoise (Ned.)

Risks

Stone can discolor to green with wear or contact with oils and grease

Physical and Chemical Properties

  • Triclinic system, opaque, dense, cryptocrystalline to fine-grain massive.
  • Fracture is conchoidal.
  • Luster = waxy.
  • Streak = white to pale-green.
  • Soluble in hot hydrochloric acid.
Composition CuAl6(PO4)4(OH)8 - 4H2O
Mohs Hardness 5 - 6
Density 2.6-2.9 g/ml
Refractive Index 1.61; 1.62; 1.65

Raman (MFA)

Turquoise, Reyston NV.PNG

Raman (MFA)

Turquoise Raman.jpg


Comparisons

Properties of Common Gemstones

Resources and Citations

  • Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
  • R.F.Symmes, T.T.Harding, Paul Taylor, Rocks, Fossils and Gems, DK Publishing, Inc., New York City, 1997
  • A.Lucas, J.R.Harris, Ancient Egyptian Materials and Industries, Edward Arnold Publishers Ltd., London, 4th edition, 1962
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
  • Encyclopedia of Archaeology, Glyn E. Daniel, ed., Thomas Y. Crowell Co., New York, 1977
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 833
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979

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