Andalusite

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Andalusite, an aluminum silicate, derives its name from the southern Spanish province of Andalusia, long believed to be the sight of its original discovery. Many now feel the original find may have actually occurred in El Cardoso, a different province in Spain, but the name endured. While andalusite's color play has been compared to alexandrite, this is technically incorrect, as it is pleochroic rather than color changing. Prized for its strong pleochroism, it displays different colors in different directions and features all its colors at once, whereas true color-change gems like alexandrite only change color when exposed to different light sources.

Andalusite Polished
Andalusite Classification
Common Name Andalusite
Species Andalusite
Andalusite Optical Properties
Transparency Transparent - Opaque
Dispersion Strength: Weak Fire Value: 0.016
Refractive Index 1.634-1.643
Tolerance:(+0.005/-0.005)
Birefringence 0.007-0.013
Optic Character Biaxial
Optic Sign Negative
Polariscope Reaction Doubly Refractive (DR)
Fluorescence SWUV: Inert to moderate green to yellowish green
LWUV: Inert
Pleochroism Trichroic, strong yellowish green, green and brownish red
Andalusite Characteristic Physical Properties
Hardness 6.5-7.5
Streak White
Specific Gravity Typical:3.170
Toughness Varies
Inclusions Andalusite is a type II clarity stone. The needles or crystals seen in the stone are most likely rutile and apatite.
Luster Vitreous
Stability Good
Fracture Uneven
Cleavage Good, in one direction, Poor, in one direction
Andalusite Chemistry & Crystallography
Chemical Name aluminum silicate
Chemical Formula Al2SiO5
Crystal System Orthorhombic
Chemistry Classification Silicate

Andalusite Colors

  • Colorless Andalusite Colorless
  • Brown Andalusite Brown
  • Green Andalusite Green
  • Multi-color Andalusite Multi-color
  • Brown Andalusite Brown
  • Pink Andalusite Pink
  • Gray Andalusite Gray

Alternate Names

Viridine, Chiastolite

Countries of Origin

Unknown; Sri Lanka; China; Brazil; Madagascar

History

The warm appeal of andalusite makes it ideal for fall and winter months, but it is beautiful throughout every season. Andalusite is pleochroic and may flash pink against gold or a golden pinkish-brown, making it the perfect choice for carefree spring and summer fashions. Prized for its strong pleochroism, andalusite displays different colors in different directions and features all its colors at once. This intriguing stone is an excellent addition to your jewelry wardrobe and works well in any gem lover's collection.

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More About Andalusite

A lesser-known gemstone, there's some evidence that andalusite was worn as an amulet in ancient cultures and used in medicinal rituals in others. Some folklore suggests that historically, it was believed that those attracted to andalusite may be fighters. However, it was thought by other cultures that, when andalusite is worn, it helps turn a fighter into a peacemaker.

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Species/Variety

Chiastolite

Chiastolite is an opaque variety of andalusite that exhibits a unique cross-like pattern, an internal characteristic caused by carbonaceous inclusions. Sometimes called the "cross stone," this formation is seen in cross-sections of the crystal. Slices are often polished as amulets or for collecting, with no two exactly alike.

Chiastolite Andalusite
Chiastolite Classification
Common Name Chiastolite
Chiastolite Optical Properties
Refractive Index 1.63-1.64
Pleochroism Unobservable
Chiastolite Characteristic Physical properties
Specific Gravity 3.13
Tim Matthews

Author

Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.