Andalusite
Description
An aluminum silicate mineral that was named for the southern Spanish province of Andalucia where it was first reported in 1789. Andalusite is mined in Spain, South Africa, Australia, Brazil, Sri Lanka,and the U.S.(California, Nevada, Maine, Pennsylvania, Massachusetts and Connecticut). The stone is pleochroic and can exhibit a pink, gray, green, red, or bluish colors sometimes appearing to be iridescent. Andalusite occurs as either transparent or opaque stones with the clear stones used as a gems. It has also been used in the manufacture of Porcelain and refractory ceramics. One variety of andalusite is chiastolite. Chiastolite contains carbonaceous impurities oriented along the crystalline axes that produce a checkered pattern.
Synonyms and Related Terms
chiastolite; ; viridine (green); kanonaite (greenish-black); aluminum silicate; Andalusit (Deut.); andalousite (Fr., Port.); andaluzyt (Pol.); andalucita (Esp..); andalusiet (Ned.)
Physical and Chemical Properties
- Orthorhombic crystal system usually found as coarse prisms or in masses
- Cleavage = good in one direction
- Fracture = uneven to subconchoidal
- Luster= vitreous
- Streak = white or colorless
- Fluorescence = inert (LW); possible weak to moderate green to yellowish green (SW)
- Pleochroism = very strong, generally light yellowish green and dark brownish red
- Dispersion = very strong
- Double refraction
| Composition | Al2O3SiO2 |
|---|---|
| Mohs Hardness | 6.5 - 7.5 |
| Density | 3.16-3.20 g/ml |
| Refractive Index | 1.63; 1.64; 1.64 |
| Birefringence | 0.007 - 0.013 |
Resources and Citations
- Gem Identification Lab Manual, Gemological Institute of America, 2016.
- Mineralogy Database: Andalusite
- Encyclopedia Britannica, http://www.britannica.com Comment: andalusite [Accessed December 4, 2001].
- Robert Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Company, Radnor, PA, 1992
- C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
- Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
- R.F.Symmes, T.T.Harding, Paul Taylor, Rocks, Fossils and Gems, DK Publishing, Inc., New York City, 1997
- Wikipedia: Andalusite (Accessed December 4, 2001 and Dec 2022)
- Thomas Gregory, The Condensed Chemical Dictionary, Reinhold Publishing, New York, 3rd ed., 1942
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
- Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
- Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998