Andalusite (Molecule of the Month for March 1997)
The garnets comprise a family of complex silicates with widely varying chemical composition but similar structures. While everyone is familiar with dark brownish or purplish red garnets, many are unaware that garnets can occur in almost any color except blue (although there have been some recent reports of some color change garnets that are predominantly blue). Slight variations in chemical composition define the placement of a garnet within the family.
Andalusite is named after Andalusia, the province of Spain where it was first discovered.
Andalusite is pleochroic, different colors in different directions. When cutting most pleochroic gemstones, such as iolite and tanzanite, the trick is to minimize the pleochroism and maximize the single best color. Andalusite is the opposite: cutters try to orient the gem to get a pleasing mix of colors: orangey brown and a yellowish green or gold.
When they succeed, andalusite looks unlike any other gemstones, with patterns of color dancing around the facets. The best color play is seen in fancy shapes, particularly rectangular cushion shapes: in round cuts, the colors blend together.
Andalusite is mined in Brazil and Sri Lanka.
In the past andalusite was sometimes called "poor man's alexandrite" because it offers color play at a low price. But andalusite really doesn't look much like alexandrite, which changes from green to red in different light. It isn't really a color change stone at all because the colors are there at the same time.
That shouldn't diminish its appeal, especially for those who like earth tones. Andalusite offers a lot of impact for a relatively low price. Because of its color and its durability, it is especially appropriate for men's jewelry
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for March 1997 )