Tanzanite

The name Tanzanite( after Tanzania) was introduced by the New York Jewelers Tiffany & co. In good quality the color from ultra marine to sapphire blue; in aritificial light it apears more amethyst voilet. 

When heated to 752-932 degrees F, the interferring yellowish and brown tints vanish, the blue deepens. Green Tanzanite is rare.