Tanzanite is a blue gemstone that can range in colour from light blue through royal blue to violet. It is a thousand times rarer than diamonds and only mined in Tanzania.
Tanzanite gemstones have a hardness of 6.5 on the MOHRs scale of mineral hardness with diamond being at the hard end of the scale with a hardness value of 10. Ruby and Sapphire come in a close second with a hardness of 9 and emerald just a touch lower at 7.5-8.
Its refractive index (speed light travels through the Tanzanite) of 1.7 being similar to that of sapphire and ruby. As a point of comparison, diamonds are around 2.4.
The Tanzanian government have for the last two decades protected their countries mining and stone processing interests with 50% of mining activity being restricted to locals and all stones over 1g rough/ unprocessed weight now being cut in Tanzania.
Tanzanite is thought to promote awareness and a heightened consciousness.