Tanzanite

In 1967, a new gemstone is discovered near Arusha, in Tanzania. It is transparent, and of a blue-purplish colour. These crystals have a pleochroism marked according to the three directions of crystallisation, i.e. sapphire blue, purple, and yellow-green. By heating, the purple and yellow-green streaks decrease in intensity and the colour blue is reinforced. Very few blue zoisites are currently available on the market, and this gemstone is highly appreciated by collectors.