Oliver has developed an interest in gemstones since living in Tanzania (and who wouldn't!!). Particularly Tanzanite.
Yesterday we visited the offices/shop of the Tanzanite Experience in Arusha.
Tanzanite is the blue/purple variety of the mineral zoisite (a calcium aluminium hydroxyl Sorosilicate) belonging to the epidote group. It was discovered in the Mererani Hills of Manyara Region in Northern Tanzania in 1967, near the city of Arusha and Mount Kilimanjaro. Tanzanite is used as a gemstone, and naturally-formed tanzanite is extremely rare, still found only in the Mererani Hills.
Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet and burgundy depending on crystalorientation. Tanzanite can also appear differently when viewed under alternate lighting conditions. The blues appear more evident when subjected to fluorescent light and the violet hues can be seen readily when viewed under incandescent illumination. Tanzanite is usually a reddish brown in its rough state, requiring artificial heat treatment to bring out the blue violet of the stone.
The mineral was named by Tiffany & Co. after Tanzania, the country in which it was discovered. In 2002, the American Gem Trade Association chose Tanzanite as a December birthstone, the first change to their birthstone list since 1912. (Wikipedia)
I learnt yesterday that the mining of Tanzanite may only last another 20 years, then the source (and there is only one place it is found) will be depleted. Oliver will have to buy up now!!