Andalusite

Big Photo

Brazil
1.25 carats
© Rarestone

Andalusite is named after the Spanish province Andalusia where transparent gem-quality crystals were first found.

Faceted andalusite stones give a play of red, green, and yellow colours because of strong pleochroism.

Andalusite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 
 
 

Andalusite Gemstones by Size

This table shows distribution of Andalusite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.19 cts
Heaviest:11.70 cts
Average:2.21 cts
Total photos:34
Do you have a larger Andalusite? Why not upload a photo?
0.19ct to 1.34ct1.34ct to 2.49ct2.49ct to 3.64ct3.64ct to 4.79ct4.79ct to 5.95ct5.95ct to 7.10ct7.10ct to 8.25ct8.25ct to 9.40ct9.40ct to 10.55ct10.55ct to 11.70ct
General Information
Varieties/Types:
Chiastolite - Crystals of Andalusite containg cross-shaped inclusions of carbon.
Viridine - A manganese-bearing, green Andalusite.
Chemical Formula
Al
 
2
SiO
 
5
Michael O’Donoghue, Gems, Sixth edition (2006)
More from other references
Photos of natural/un-cut material from mindat.org
Andalusite Treatments
It is reported that olive-green material from Brazil changes to pinkish when heated (Sinkankas, 1972), while brown material is reported (Smith et al, 1978) to fade above 800°C to colorless. Irradiation could conceivably reverse these changes (Nassau, 1984
Physical Properties of Andalusite
Mohs Hardness7.5
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Specific Gravity3.05 to 3.21
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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TenacityBrittle
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityGood
Walter Schumann, Gemstones of the world (2001)
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FractureUneven
Arthur Thomas, Gemstones (2009)
Heat SensitivityYes
Arthur Thomas, Gemstones (2009)
Optical Properties of Andalusite
Refractive Index1.627 to 1.650
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Optical CharacterBiaxial/-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Birefringence0.007 to 0.013
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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PleochroismOrange/brown stones - strong trichroism: yellow - olive green - reddish brown; Yellow stones - strong: yellow - olive-green - red-brown; Green stones - strong: yellow - olive green - red-brown
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Dispersion0.016
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)Green, yellowish-green, brown, pink, colourless
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Causes of ColourGreen and brown, pleochroism Fe2+ -O- Ti4+ charge transfer. Dark green, Mn3+ in octahedral coordination
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTransparent,Translucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreVitreous
Arthur Thomas, Gemstones (2009)
Fluorescence & other light emissions
Fluorescence (General)Weak; green, yellow-green
Walter Schumann, Gemstones of the world (2001)
Fluorescence (Short Wave UV)Inert to moderate green to yellowish green
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Fluorescence (X-RAY)The brownish greenstones from Brazil often show greenish yellow under X-rays.
Michael O’Donoghue, Gems, Sixth edition (2006)
Crystallography of Andalusite
Crystal SystemOrthorhombic
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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HabitPrismatic habit with vertically striated prisms which are nearly square in section and capped with pyramids
Michael O’Donoghue, Gems, Sixth edition (2006)
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Geological Environment
Where found:A result of contact metamorphism of argillaceous sediments, also in regionally metamorphosed schists. Rare in granites and pegmatites, which however afford the largest crystals. Detrital in some sandstones.
Anthony et al., Handbook of mineralogy (2003)
Inclusions in Andalusite
Rutile needles - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 4
Needle-like crystals, liquid inclusions - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 16
Further Information
Mineral information:Andalusite information at mindat.org
Significant Gem Localities
Australia
 
  • South Australia
    • Olary Province
      • Kalabity homestead area
[var: Chiastolite] Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 381
Brazil
 
  • Minas Gerais
    • Diamantina
    • Itinga
Madagascar
 
  • Fianarantsoa Province
    • Horombe Region
      • Ihosy District
        • Ilakaka Commune
Madagascar - extraLapis English No.1, p. 92
Myanmar
 
  • Mandalay Region (Mandalay Division)
    • Pyin-Oo-Lwin District
      • Mogok Township
        • Kyauk-Pyat-That
Ted Themelis (2008) Gems & mines of Mogok
        • Mogok Valley
Ted Themelis (2008) Gems & mines of Mogok
        • Pein-Pyit (Painpyit; Pyan Pyit)
Ted Themelis (2008) Gems & mines of Mogok
Ted Themelis (2008) Gems & mines of Mogok
Sri Lanka
 
  • Sabaragamuwa Province
    • Ratnapura District
      • Ratnapura
USA
 
  • California
[var: Chiastolite] Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 382
  • Colorado
    • Gunnison Co.
      • Box Canyon District
U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
Copyright © Jolyon & Katya Ralph 1993-2017. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.