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'Andalusite' is an aluminium nesosilicate mineral with the chemical formula Al₂SiO₅.
The variety chiastolite commonly contains dark inclusions of carbon or clay which form an ''X'' or a cross in section.
A clear variety first found in Andalusia, Spain can be cut into an interesting gemstone.^[2] Faceted andalusite stones give a play of red, green, and yellow colors that resembles a muted form of iridescence, although the colors are actually the result of unusually strong pleochroism.

Contents

Occurrence

Related minerals

See also

References

Notes

Occurrence

Andalusite is a common regional metamorphic mineral which forms under high pressure and/or temperature. The minerals kyanite and sillimanite are polymorphs of andalusite, each occurring under different temperature-pressure regimes and are therefore rarely found together in the same rock. Because of this the three minerals are a useful tool to help identify the pressure-temperature paths of the host rock in which they are found.
It was first reported from Andalucia, Spain in 1789.

Related minerals

★ Kyanite

★ Sillimanite

★ Chiastolite

See also

★ List of minerals

References

★ Mineral galleries

★ Webmineral

★ Mindat w/ locations

★ http://www.gemstone.org/gem-by-gem/english/andalusite.html

Notes

1. Gemological Institute of America, ''GIA Gem Reference Guide'' 1995, ISBN 0-87311-019-6
2. ''International Colored Gem Association: Anadalusite''