Tanzanite
Tanzanite
Tanzanite is the gemological name for the blue to violet variety of zoisite, a stone whose color is linked to the presence of vanadium in the stone.
Remarkably, it is found in only one area in the world, the Merelani hills in northern Tanzania, near Mount Kilimanjaro.
Tanzanite is famous for its very pronounced pleochroism: by tilting it, several colors can be observed depending on the direction of the crystal, typically blue and purple (and sometimes a brownish-yellow component).
This characteristic directly influences the size, because the orientation chosen by the lapidary determines whether the gem will appear more blue-violet or more violet-blue.
In the trade, many tanzanites are heated: this treatment easily removes brownish tones and highlights a duo of hues dominated by blue and purple.
We can therefore speak of “varieties” mainly in the sense of shades (lavender, deep purple, deep blue), the most saturated colors generally being the most sought after.
Tanzanite can also exhibit color zoning (areas that are more or less blue/purple), a true trace of its growth.
It is important to note that zoisite also exists in other colours (colourless, yellow, green, pink), but these stones should not be called “tanzanite” with a colour adjective if blue/violet does not clearly dominate.
In terms of resistance, its hardness is around 6 to 7 on the Mohs scale, making it suitable for jewelry, while requiring a minimum of care on a daily basis.
For maintenance, opt for gentle cleaning (warm soapy water, cloth) and avoid impacts as well as aggressive products.
Ultimately, tanzanite is an exciting stone because it directly links trace element chemistry and the physics of light: a few well-placed atoms are enough to create a unique, almost "changing" blue-violet.