Andalusite

Andalusite Information

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CHEMISTRY Al2SiO5 + Fe
CRYSTALLOGRAPHY Orthorhombic
REFRACTIVE INDEX 1.629 - 1.650
HARDNESS 6.5 - 7.5
SPECIFIC GRAVITY 3.13 - 3.17
CLEAVAGE Distinct one direction
HEAT SENSITIVE No

WEARABILITY* Very Good
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS Can be heat treated to improve color. Rarely done.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."

... Andalusite is a strongly pleiochroic gem, which means that is has different colors when viewed from different directions. While it is a strikingly beautiful gem, is largely unknown by the gem buying public.
... It's trichroic nature, which shows shades of brown, green and reddish brown depending on the orientation of the crystal, can be enhanced by specific orientation and cut. Those cuts with a long axis such as an oval, marquis or emerald cut tend to show one color near the center and a second, usually darker color near the ends. Square and round cuts usually blend the colors into a mosaic.
... Most specimens contain some inclusions, the most common being rutile needles. Brazil is the chief producer, but Sri Lanka, Russia and the US also have deposits. Of course, so does the site of original production, Andalusia, Spain.
... Andalusite is hard and tough enough for most jewelry uses. Poorly cut and polished stones are pretty dull and insipid looking, but a large, clean, well-cut Andalusite is a show stopper!

Value

... Sinkankas places a wholesale value on small, commercial quality faceted stones at around $40 per carat for clean gems with good color. Larger stones and those with custom cuts fetch up to $200 per carat. Federman doesn't give an exact price range, but suggests that, next to other gemstones one might find in good jewelry, they are "reasonable".

Text and photos courtesy of Barbara Smigel at Artistic Colored Stones.

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