Tanzanite’s Pleochroic Colors
Tanzanite, one of December's birthstones, is a rare blue-to-violet or purple zoisite found only at the foot of Mount Kilimanjaro in Tanzania. Its color can rival that of the finest sapphire. It is a beautiful gem in its own right, however, displaying strong trichroism (or pleochroism), meaning it shows different colors when viewed in different crystal directions.
Tanzanite’s pleochroic colors are red-violet, blue and yellow-green, though most gems are heat treated now, which removes the yellow-green or brownish pleochroic color, maximizing the blue and violet. The tanzanites seen here are also bicolor, which means they have two distinct color zones, in addition to being trichroic!
Tanzanite’s pleochroic colors are red-violet, blue and yellow-green, though most gems are heat treated now, which removes the yellow-green or brownish pleochroic color, maximizing the blue and violet. The tanzanites seen here are also bicolor, which means they have two distinct color zones, in addition to being trichroic!