Zoisite

Tanzanite

Tanzanite is blue-violet zoisite, mined commercially only near Merelani in Tanzania. Most stones are heated to remove a brownish tint.

Tanzanite

At a glance

Mineral: Zoisite, blue-violet; found in one area of Tanzania
Refractive index: 1.694
Dispersion (C–F): 0.012
Specific gravity: 3.35
Mohs hardness: 6–7
Wear: Softer and prone to cleavage: better in pendants and earrings, or rings with protective settings.

Tanzanite in Jart

The look in the studio's material library, with the values the renderer uses.

Optics of Tanzanite in Jart
Stone	Colour	RI	Dispersion C–F	Abbe	SG	Colour depth
Tanzanite	#7f5ee6	1.694	0.012	57	3.35	6 mm

RI refractive index (n_d). Dispersion C–F n_F − n_C, the spread between blue and red light; many gem tables quote the B–G figure instead (diamond 0.044, here 0.025). Abbe number: lower means more fire. SG specific gravity, used for carat estimates in Design Facts. Colour depth the path through the stone after which white light takes the stone's full colour; shorter paths look paler.

How it renders

With a refractive index of 1.694, a polished tanzanite facet reflects 6.6% of light that meets it face-on (diamond: 17.2%). Light inside the stone that meets a facet more than 36.2° from straight on cannot leave and is reflected back in; the smaller that angle, the more light a good cut returns to the eye (diamond 24.4°, quartz 40.4°).

Its dispersion (C–F) is 0.012, 49% of diamond's, which sets how much fire, the flashes of colour, a render shows under small, bright lights.

Real tanzanite shows blue, violet and sometimes burgundy depending on the viewing direction (pleochroism). Jart renders its blue-violet face-up colour; direction-dependent colour is not simulated yet.