Tanzanite is the name given to transparent blue zoisite. It is quite a ‘new’ stone, having been discovered in Tanzania by the Masai tribe in 1967. Tanzanite crystals have been growing for millions of years in deposits on the inside of metamorphic hills on a vast plain in the shadow of Kilimanjaro. They were noticed one day by a group of Masai shepherds who noticed the sparkling crystals lying in the sun. They were introduced to the jewellery world in 1969 by Tiffany and Co., who named them after their discovery location to add to their exotic appeal.
It is usually found in varying shades of blue, from pale and lilac to deep violet and navy, but can occasionally also be green, yellow, pink and brown. However, as the blue is the most popular variety for use in fine jewellery, the other-coloured stones and paler blues are usually heat-treated to produce the deep blue colour.
The Masai believe that Tanzanite is the stone of birth because of its blue colour, and they give tanzanite to their wives at the birth of their first-born children.
One of the largest refined specimens of tanzanite, named ‘The Midnight Blue’, is 122.7 carats and is located at the Natural History Museum in Washington DC.