Turquoise

WHAT IS IT?

  • A hydrated (water containing) phophate of copper and aluminum

  • Chemical formula: CuAl6(PO4)4(OH)8·4H2O

  • Mho hardness of 6 for fine grained specimens, lower for large grain sizes (5-6)

  • Forms when acidic solutions come in contact with other minerals

  • Usually formed in arid climates at shallow depths (< 20 meters)

  • Igneous

  • Similar to feldspar

  • Rarely occurs in crystalline form (crystalline turquoise is found at the Bishop mine, Lynch Station, Virginia & in Nevada, New Mexico, & Pennsylvania) always microscopic

  • Found in masses

  • Has a slightly conchoidal fracture (shell-like)

  • Opaque, but thin slices can be semitranslucent

  • Most desirable colors: blue & green

  • Often found in matrix

  • Damaged by sunlight (causes fading), acids (fatty acids from soap), oils, perfume

INTERESTNG FACTS

  • The birthstone for December

  • The name comes from the French word for "Turkish" because it was believed that turquoise was mined in Turkey (It wasn't— it was only traded)

WHERE IS IT FOUND?

  • United States (Alabama, Arizona, California, Colorado, Nevada, New Jersey, New Mexico, Texas, Virginia, Wisconsin, Wyoming), Egypt (Sinai Peninsula & Red Sea coast), Iran, Afghanistan, Saudi Arabia, Tibet, China, Germany, France, Spain, Australia, Peru, Chile, Mexico

TYPES

There are many turquoise types. They are usually named after the place where they are mined or by a specific characteristic, but sometimes have unique names. There are many imitations also (glass/enamel, synthetics, substitutes).

  • Named after mines — Dry Creek, Carico Lake (Lander County, NV), Lone Mountain (Esmeralda, NV)

  • Named for the location — Kingman (Kingman, AZ — has been mined for over 100 years by Navajo Indians), Bisbee (Bisbee, AZ), Persian

  • Unique names — Royston (Tonapah, NV), Sleeping Beauty (Globe, AZ), Larimar Stone (also called Stefilia's Stone)

WHAT IT USED FOR?

  • Prized for ornamental use since ancient times (ancient Egypt, Aztec, Persian, Indus cultures)

  • Native Americans craft beautiful jewelry from turquoise & silver

  • Medical uses — it was thought to change color with the wearer’s health & provide protection

  • Had many superstitious uses — prevented falls from horses (Persia), brought happiness & prosperity (India)