Aquamarine

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Aquamarine
Aquamarin cut.jpg
Aquamarine
General
Category beryl mineral variety
Chemical formula Be3Al2Si6O18[1]
Identification
Color transparent (or can be translucent if included), greenish blue to blue green, typically light in tone
Crystal system hexagonal
Cleavage very difficult in one direction, almost never seen
Fracture conchoidal
Mohs Scale hardness 7.5-8
Luster vitreous to resinous
Refractive index 1.577 - 1.583 (+/- .017)
Optical Properties Double refractive, uniaxial negative
Birefringence .005 - .009
Pleochroism weak to moderate, blue and greenish blue; or different tones of blue with lighter tones associated with the optic axis direction
Specific gravity 2.72 (+.18, -.05)

Aquamarine (Lat. aqua marina, "water of the sea") is a gemstone-quality transparent variety of beryl, having a delicate blue or turquoise color, suggestive of the tint of seawater. It is closely related to the emerald. Colors vary—yellow beryl, called heliodor; rose pink beryl, known as morganite; and white beryl, called goshenite, are known.

Contents

Occurrence

This mineral occurs at most localities that yield ordinary beryl, some of the finest coming from Russia. The gem-gravel placer deposits of Sri Lanka contain aquamarine. Clear yellow beryl, such as occurs in Brazil, is sometimes called aquamarine chrysolite. When corundum presents the bluish tint of typical aquamarine, it is often called "oriental aquamarine."

In the United States, aquamarine can be found at the summit of Mt. Antero in the Sawatch Range, in central Colorado. It is the official state gem of Colorado.

In Brazil, there are mines in the states of Minas Gerais, Espírito Santo, and Bahia. Attractive aquamarine stones are also produced by Zambia, Madagascar, Malawi, Tanzania, and Kenya.

The biggest aquamarine ever mined was found at the city of Marambaia, Minas Gerais, Brazil, in 1910. It weighed over 110 kg, and its dimensions were 48.5 cm long and 42 cm in diameter.

Characteristics

Aquamarine is a type of beryl with a hexagonal crystal structure and a chemical formula of Be3Al2Si6O18, a beryllium aluminum silicate mineral. It has a specific gravity of 2.68 to 2.74 and a Mohs hardness from 7.5 to 8. Aquamarine, typically, is on the low end of the specific gravity range, normally at less than 2.7. The pink variety exhibits a high specific gravity of around 2.8. Refractive indices ranging around 1.57 to 1.58.

Much of today's aquamarine is heated to give it a better color blue. The deeper the blue color, the more valuable the gem is considered.

Cultural and historical/mythical usage

  • Aquamarine is the birthstone associated with March. It is also the gemstone for the 19th Anniversary.
  • People in the Middle Ages thought that aquamarine could magically overcome the effects of poison.
  • Ancient sailors traveled with aquamarine crystals, believing that it would ensure a safe passage, and often slept with the stones under their pillow to ensure sound sleep. They believed the siren’s (mermaid) fish-like lower body was made of aquamarine.

Alternative meaning

Aquamarine is also the name for a color, which is a shade between green and blue.

Notes

  1. Gemological Institute of America, GIA Gem Reference Guide (1995). ISBN 0-87311-019-6

References

  • Farndon, John. 2006. The Practical Encyclopedia of Rocks & Minerals: How to Find, Identify, Collect and Maintain the World's best Specimens. Lorenz Books. ISBN 0754815412
  • Hurlbut, Cornelius S. and Klein, Cornelis. 1985. Manual of Mineralogy, 20th ed. New York: John Wiley and Sons. ISBN 0-471-80580-7
  • Pellant, Chris. 2002. Smithsonian Handbooks: Rocks and Minerals. New York: DK Adult. ISBN 0789491060
  • Shaffer, Paul R., Herbert S. Zim, and Raymond Perlman. 2001. Rocks, Gems and Minerals. St. Martin's Press, Golden Guide. ISBN 1582381321
  • Weinstein, Michael. 1967. The World of Jewel Stones. New York: Sheridan House.

External links

All links retrieved October 25, 2012.

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