Prasiolite

Prasiolite
General
Category Oxide mineral
Crystal system Trigonal
Identification
Color shades of green
Crystal habit Hexagonal prisms
Cleavage None
Fracture Conchoidal[1]
Tenacity brittle[1]
Mohs scale hardness 7 – lower in impure varieties[1]
Diaphaneity Transparent to nearly opaque
Specific gravity 2.65
Refractive index 1.544 to 1.553[2]
Birefringence 0.009[3]
Ultraviolet fluorescence none

Prasiolite (also known as green quartz or vermarine) is a green variety of quartz, a silicate mineral chemically silicon dioxide.

Since 1950, almost all natural prasiolite has come from a small Brazilian mine, but it is also seen in Lower Silesia in Poland. Naturally occurring prasiolite is also found in the Thunder Bay area of Canada.[4]

Most prasiolite sold is used in jewellery settings, where it can substitute for far more expensive precious gemstones.

It is a rare stone in nature; artificially produced prasiolite is heat treated amethyst.[4] Most amethyst will turn yellow or orange when heated producing citrine. But some amethyst will turn green when treated. Currently, almost all prasiolite on the market results from a combination of heat treatment and ionizing radiation.[5]

Green quartz is sometimes incorrectly called green amethyst, which is not an acceptable name for the material, the proper terminology being prasiolite.[6] It is actually against Federal Trade Commission Guidelines to call prasiolite "green amethyst." Other names for green quartz are vermarine, greened amethyst, or lime citrine.

The word prasiolite literally means "scallion green-colored stone" and is derived from Greek πράσον prason meaning "leek" and λίθος lithos meaning "stone." The mineral was given its name due to its green-colored appearance.

Natural prasiolite is a very light, translucent green. Darker green quartz is generally the result of artificial treatment.[7]

See also

References

  1. 1 2 3 Prasiolite on Gemdat.org
  2. ↑ Lazarelli. Blue Chart Gem Identification. p. 7.
  3. ↑ http://www.galleries.com/Prasiolite
  4. 1 2 "Prasiolite". quarzpage.de. 28 October 2009. Retrieved 28 November 2010.
  5. ↑ "Mineral Spectroscopy Server". California Institute of Technology. 11 June 2012. Retrieved 10 December 2012.
  6. ↑ "Green Amethyst". GemSelect. Retrieved 10 December 2012.
  7. ↑ Gems and Gemstones: Timeless Natural Beauty of the Mineral World By Lance Grande, Allison Augustyn, p.91


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