TANZANITE
Tanzanite is the blue to violet-blue variety of the mineral zoisite. Found only in the Merelani Hills of northern Tanzania, near Mount Kilimanjaro, it is one of the most recently discovered gemstones to achieve widespread popularity. The name ‘tanzanite’ was introduced by Tiffany & Co. in reference to its country of origin, replacing the mineralogical term ‘blue zoisite’ with a name that would distinguish and market the gemstone to a wider audience.

History of Tanzanite
Tanzanite is a relatively recent addition to the world of coloured gemstones. In 1967, a Maasai tribesman discovered a cluster of highly transparent crystals in shades of intense violet and blue in the Merelani Hills of northern Tanzania. He brought the discovery to Manuel D’Souza, a local prospector, who quickly registered four mining claims, initially believing that he had found a new source of sapphire. The deposit, however, proved to contain a new gem variety.

The discovery sparked a rush of interest, with around 90 additional claims soon being registered across the same 20-square-mile area. The gemstone was eventually named tanzanite, after Tanzania, and its vivid blue-to-violet colour, high clarity and ability to produce large cut stones quickly attracted international attention. Tiffany & Co. recognised its commercial potential and became its principal distributor, launching a major publicity campaign in 1968. Tanzanite soon gained popularity among jewellery designers, gem professionals and collectors, establishing itself as a distinctive new gemstone.

The Merelani Hills near Arusha remain the world’s only known commercial source of tanzanite. Its single-source origin and concerns that the deposits may eventually be depleted have contributed to its appeal. Its striking colour and scarcity have also encouraged designers to experiment with different shapes and cuts to highlight its optical qualities.

Colour and Characteristics of Tanzanite
Tanzanite is best known for its rich blue to violet-blue hues, ranging from pale blue and lavender to intense violetish blue and deep blue-violet. The most valued colours are generally deeply saturated violet-blue and blue-violet. The gemstone's colour is particularly distinctive because of its strong pleochroism, meaning that it can display different colours when viewed from different directions. In rough crystals, these colours can include blue, violet and reddish or burgundy tones.

The final colour of a cut stone depends partly on the orientation chosen by the cutter. Much of the tanzanite available in the market is heated to enhance or produce its blue colour. Heating can transform or intensify the colour of naturally brownish or other less desirable zoisite, while naturally blue, untreated tanzanite is comparatively rare.

Tanzanite has a vitreous lustre and is generally transparent, often displaying good clarity. It has a Mohs hardness of approximately 6 to 7 and a specific gravity of 3.35. Tanzanite requires care when worn as jewellery, particularly in rings that are exposed to impact. It can be worn in different types of jewellery with appropriate care, but earrings, pendants and other pieces where the stone is less exposed to hard blows are generally less vulnerable to damage.