Moonstone (gemstone)

Moonstone is a sodium potassium aluminium silicate ((Na,K)AlSi3O8) of the feldspar group that displays a pearly and opalescent schiller.[1][2] An alternative name is hecatolite.[2]

Not to be confused with Moon rock.
For other uses, see Moonstone (disambiguation).
Moonstone
General
CategoryOrthoclase variety
Formula
(repeating unit)		(Na,K)AlSi3O8
Identification
ColorCan be numerous colors, including blue, grey, white, pink, peach, green and brown, as well as colorless
Fractureuneven to conchoidal
Mohs scale hardness6.0
LusterOpalescent
Streakwhite
Specific gravity2.61
A small raw moonstone from an unknown area.

Etymology

Its name is derived from a visual effect, sheen or schiller (adularescence), caused by light diffraction within a micro-structure consisting of regular exsolution layers (lamellae) of different alkali feldspars (orthoclase and sodium-rich plagioclase).

History

Moonstone has been used in jewelry for millennia, including ancient civilizations. The Romans admired moonstone, as they believed it was derived from solidified rays of the Moon.[3] Both the Romans and Greeks associated moonstone with their lunar deities. In more recent history, moonstone became popular during the Art Nouveau period; French goldsmith René Lalique and many others created a large quantity of jewelry using this stone.[4]

Geology

The most common moonstone is of the orthoclase feldspar mineral adularia, named for an early mining site near Mt. Adular in Switzerland, now the town of St. Gotthard.[1] A solid solution of the plagioclase feldspar oligoclase +/− the potassium feldspar orthoclase also produces moonstone specimens.

Occurrence
Polished moonstone cabochon

Deposits of moonstone occur in Armenia (mainly from Lake Sevan), Australia, the Austrian Alps, Mexico, Madagascar, Myanmar, Norway, Poland, India, Sri Lanka[5] and the United States.[2]

The moonstone is the Florida State Gemstone; it was designated as such in 1970 to commemorate the Moon landings, which took off from Kennedy Space Center. Despite it being the Florida State Gemstone, it does not naturally occur in the state.[6]

References
  1. Moonstone Gemological Information International Gem Society, Retrieved 01-05-15
  2. Moonstone on Mindat.org
  3. "Moonstone" American Gem Trade Association. Retrieved 21 January 2011.
  4. "Moonstone" International Colored Gemstone Association. Retrieved 26 April 2012.
  5. "Moonstone" Encyclopædia Britannica, 2011. Web. 20 Jan. 2011.
  6. "Moonstone - Florida State Symbols". Florida Division of Historical Resource. Retrieved 1 Sep 2011.
  • Media related to Moonstone at Wikimedia Commons
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