Tanzanite.

Tanzanite was discovered in 1967 and named after the place of extraction. He became famous thanks to the American jewelry company "Tiffany", thanks to a competent advertising policy, rarity, beauty of color and Elizabeth Taylor, who loved jewelry made of stone. Deep blue, blue-violet, purple and yellow-brown colors are used in jewelry, with special preference for stones with ultramarine and sapphire blue. Under electric light, it takes on an amethyst purple hue. The Tanzanite Foundation mining company has developed its own color grading scale. In which they are distinguished: from bluish-violet, indigo to violet-blue. The normal primary and secondary shades of tanzanite are blue and purple. This color is achieved by thermal treatment of the mineral up to 500-600 degrees Celsius. The purity of the stone is considered to be "by eye" under the condition of 20/20 vision, a stone is considered flawless if no inclusions are visible to the naked eye.