Tanzanite is a variety of zoisite. It has naturally occurring shades of blue, green, yellow, pink, brown and khaki but virtually all gemstone quality crystals are heat treated to produce the highly valued shades of sapphire blue, amethyst and blue violet. On Mohs’ scale of hardness, tanzanite is 6.5-7. The prime source of all the world’s tanzanite is in Tanzania near Arusha.
Color
Tanzanite has naturally occurring shades of blue, green, yellow, pink, brown and khaki but virtually all gemstone quality crystals are heat treated to produce the highly valued shades of sapphire blue, amethyst and blue violet.
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