Underground crystal to world-renowned rock star, Tanzanite’s story is an inspiring one for all undiscovered minerals. There’s no doubt that this gem has earned its super-stardom thanks to natural trichroic talents, but the helping hand of manager Tiffany & Co is what brought Tanzanite jewellery overnight fame.
First discovered in 1967 by a Masai tribesman in Merelani, northern Tanzania, this fresh-faced gem was quickly picked up by Tiffany & Co who recognised the gemstone’s potential as a headliner and became the main distributor. Tanzanite is a variety of Zoisite, which is a member of the Epidote group, and owes its unique colour to trace elements of Vanadium. Tanzanite’s colour can vary from vivid blue to lavender purple but it’s this stone’s pleochroism that sets it apart from other similarly coloured gems.
Pleochroism refers to a crystal’s ability to display different colours depending on the crystal axis it is viewed from. This optical phenomenon results in ‘differential selective absorption’ (where wavelengths of white light are absorbed differently due to a crystal’s internal chemical structure). Tanzanite is an orthorhombic crystal and displays trichroism, meaning it displays three different colours from three different crystal axes. Typically found in a yellowish-brown “bug-juice” colour, the majority of blue Tanzanite’s on the market have been subject to heat treatment to cancel out the yellowish-brown tones and further enhance the blue/violet hues. Although it is possible to find naturally occurring blue crystals, it is extremely rare. Even still, these natural blue Tanzanite’s are still heated but from a mechanical geological action rather than a lab process. Unheated stones show trichroic colours of purplish red, blue and green/yellow, the green/yellow portion is not observed in heated stones. These results are a way of identifying heated and unheated stones.
Pleochroism influences a Tanzanites colour and some faceted stones may show flashes of both blue and reddish purple when slowly tilted from side to side. This remarkable colouring attribute has helped it gain such quick popularity, rivalling the likes of the classic blue Sapphire. The challenge for stonecutters is to capture this amazing colour play whilst still retaining carat weight and clarity when orienting the crystal for faceting. Vivid blue Tanzanite rings are the most desirable but as the blue colour is viewed from the short axis of the crystal it is not the most economical orientation to cut from in order to gain the most yield out of the rough, and for this reason most Tanzanite gemstones exhibit a more purple/violet colour.
Tanzanite can be found in eye-clean quality but are known to have fine healed fractures, this along with a hardness of only 6 ½ (MOH’s scale), paired with perfect prismatic cleavage, make it a problematic mineral to cut and set. (Cleavage refers to a stone tendency to ‘cleave’ or ‘split’ along certain crystallographic structural planes due to a weakness in their atomic bonds).
Bunny Bedi, owner and designer at Made in Earth, has included this icon in his vast collection. “Tanzanite is found exclusively in Tanzania but luckily for us most tanzanite rough is being cut in India so we have access to stones. Although it’s common practice for Tanzanite to undergo heat treatment it is still not a guarantee that all brown rough will produce the desired blue/violet colour. We have found some bi-coloured stones with yellow/green colour zoning and although they are not ‘traditionally beautiful’ we’ve found them to be quite interesting specimens for our Tanzanite jewellery collection.”
Tanzanite is the new kid on the block but has made waves through the jewellery industry, gathering a worldwide following along the way. Its colour is more complex than others in the ‘precious gemstone’ category and although tanzanite requires special treatment to showcase its true colours, we can still appreciate its natural talents. Known as ‘the stone of magic’, you too can appreciate the magic of its beauty when viewing our range of Tanzanite pendants, rings, and earrings.