As the yellow and brown shades in Tanzanite are considered less desirable features, heating is a common technique, applied to most tanzanites to bring out a more radiant blue.
As its name reveals, the blue variety of zoisite, the so-called Tanzanite was first unearthed in 1967 near Arusha, Tanzania, not far from Mount Kilimanjaro. The beautiful gem belongs to one of the more recently discovered gem varieties, which have only started awakening curiosity and attracting attention recently. Due to the blue gemstone’s scarce occurrence, it is highly priced and the probable future exhaustion of mines adds to even higher pricing.
Long known by geologists, zoisite is a silicate of calcium and aluminium, encompassing a variety of colourful minerals.
The tanzanite, which owes its fine blue colour to traces of vanadium and/or chromium, is sometimes compared to blue sapphire, but distinguishable by its strong pleochroism. This gemstone shows a strong pleochroism, its colour varies depending at which angle the stone is viewed between pinkish-purple, yellowish, and a deep purplish blue. Brown, grey and colourless, are additional colours which can be displayed in a tanzanite from different angles.
East Africa – specifically Tanzania – is the only place where tanzanite of gemstone quality is found, while other zoisite varieties are found in many places around the world. However, most of them do not produce material of gemstone quality.