Tanzanite

Tanzanite is a blue variety of the mineral zoisite gray to greenish. He is like the pink variety Thulit exclusively used as a gemstone.

Etymology and history

The first finds of transparent, purple - bluish to purple tanzanite there was in 1967 in northern Tanzania. The stone was known only by the New York jeweler Tiffany. This named him to his place of origin tanzanite, as the name zoisite reminded him too much of the English word for suicide ( "suicide ").

Education and Locations

Tanzanite is likely to form from hydrothermal solutions in corridors and chasms of gneisses.

The only minable and commercially exploited deposits of high quality tanzanite crystals is still in the Gilewy Hills near Arusha in Tanzania. The current findings, however, only rarely reach the outstanding quality of previous years.

From the region of the Hindu Kush in Pakistan, although Tansanitfunde have also been reported, but these stones reach neither the color quality or the purity of those from Tanzania and can not be forced by firing over lead in the coveted blue-violet color.

Use as a gemstone

Normally, tanzanite occurs in sizes between 0.5 and 10 carats. Rarely, there are also larger crystals and Tanzanite cat eyes. As the largest known, undamaged and untreated Tansanitkristall so far applies to the 22 centimeters high and 11,000 carats " Kilimanjaro ".

Very pronounced the multi-color ( pleochroism ) of the tanzanite in the colors dark blue, green - yellow and red - purple. The larger the stone, the more intense the color. Thanks to its unusual aura and the help of the New York jeweler 's Tiffany, it has rapidly become one of the most sought-after gemstones in the world.

Because of its high transparency, the mineral is very popular as a gemstone and high prices too. Because of its pronounced cleavage in one direction tanzanite not only reacts sensitively to pressure loads such as occur during grinding and barrel work, but also on uneven heat loads or rapid Temperaurwechsel. Already picking up the repaired item from the soldering carbon or the laying on of the piece at the brazing sheet or board Stock for cooling can lead to cracks in the stone. Nor can withstand the gemstone cleaning in the ultrasonic unit. Also on acids or acid mixtures it is sensitive.

Since the tanzanite has a relatively low Mohs hardness for gemstones from 6.5 to 7, which is lower than that of quartz ( 7), the sensitivity of the stone must be taken into account even when wearing Tansanitschmuck. Rough handling can otherwise may quickly become scratched.

Manipulation and imitation

A large part of the marketed tanzanite is produced by firing at about 400 to 500 ° C from gray -brown to yellow-brown Zoisiten. The burning also enhances the blue color pale colored stones. Tanzanite is imitated but also through colored glass ( cheap route ) or duplicates.

Synthetic Tanzanite is not yet known. In the occasionally offered on Mineral Exchanges " synthetic tanzanite " there are usually synthetic forsterite.