Before It Was Tanzanite

It’s one thing to talk about heated tanzanite and another to actually see the transformation of green/brown zoisite into its purple-blue variety. L. Allen Brown of All That Glitters, Methuen, Mass., is a veteran at heat treatment of tanzanite. He hoped to get a spectacular blue from the very slightly olive-green natural-color zoisite pictured here.

Brown says his starting material had a relatively nice green and could have been sold as a collector’s stone. The chance of getting a more salable and valuable blue tanzanite resulted in moderate heat treatment for a period of just hours, and the green zoisite was transformed into the beautiful tanzanite seen here.

It was not a complete success. “I think the green would have been better left unheated,” says Brown. Still, he now has a strongly saturated salable blue tanzanite.

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