Difference between revisions of "Alexandrite"

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[[Image:Alex-purple.gif|left|thumb|250px|Cat's eye Alexandrite under incandescent light<br />Photo courtesy of The Gem Trader]]
 
[[Image:Alex-purple.gif|left|thumb|250px|Cat's eye Alexandrite under incandescent light<br />Photo courtesy of The Gem Trader]]
 
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== G&G Articles on Alexandrite 1934-1980==
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The GIA has published all the [http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/index-back-issues-1934-80.html G&G's from 1934 until 1980 online]. The organization of the list by subject was done by [http://archive.org/details/GillsHistoricalIndexToGemsAndJewelryOnline-ByJosephO.Gill2009in Joseph Gill].
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<ul>
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/spring-1949.pdf Spring 1949, <b>The Origin of Alexandrite Color Change</b>, p. 143, 3pp.]
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</li>
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/spring-1959.pdf Spring 1959, <b>A 45 ct., a 12 ct., and a 50 ct. alexandrite</b>, p. 264, 1p.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/winter-1963.pdf Winter 1963,<b> A cat's-eye alexandrite</b>, p. 104, 2pp.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/fall-1964.pdf Fall 1964, <b>Synthetic alexandrite made</b>, p. 216, 1p.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/winter-1974.pdf Winter 1974,<b> A new synthetic alexandrite by the Czochralski Method</b>, p. 367, 3pp.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/fall-1976.pdf Fall 1976, <b>Alexandrite from Lake Manyara, Tanzania</b>, by Gübelin, p. 203, 11 pp., with bibliography]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/fall-1976.pdf Fall 1976, <b>African alexandrites?</b>, p. 211, 3pp.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/spring-1979.pdf Spring 1979, <b>Natural &amp; Synthetic Alexandrites</b>, p. 148, 1p.]
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</li></ul>

Revision as of 13:48, 13 August 2012

Alexandrite
Chemical composition Al2(BeO4)Beryllium aluminum oxide
Crystal system Orthorhombic
Habit Tabular, pseudo-hexagonal
Cleavage Imperfect prismatic
Fracture Weak, conchoidal
Hardness 8.5
Optic nature Biaxial +
Refractive index 1.744 - 1.755
Birefringence 0.009
Dispersion Low, 0.014
Specific gravity 3.70 - 3.72
Lustre Bright vitreous
Pleochroism Strong

Alexandrite is a phenomenal variety of the mineral chrysoberyl. Because of the trace amounts of the chromophores vanadium and chromium, alexandrite appears different colors depending on whether it is viewed in natural or incandescent light. In daylight, the stone appears to be green; in artificial light it appears to be raspberry red. It was originally discovered in the Ural Mountains in 1830 on the birthday of Czar Alexander of Russia. Another extraordinary coincidence was that the national colors of Russia were red and green. Today, alexandrite is found in Brazil and to a lesser extent in Africa. Alexandrite has long been associated with great luck and prosperity.

Additional Phenomena

Alexandrite image gallery

  • Cat's Eye
Cat's eye Alexandrite under daylight
Photo courtesy of The Gem Trader

Cat's eye Alexandrite under incandescent light
Photo courtesy of The Gem Trader


G&G Articles on Alexandrite 1934-1980

The GIA has published all the G&G's from 1934 until 1980 online. The organization of the list by subject was done by Joseph Gill.