01Colour

The first thing you see, and the quality that matters most. Tanzanite runs from soft lavender to a deep, velvety violet-blue; the richer and more evenly saturated the colour, the rarer the stone. Our gemologists grade it by hue — blue-violet (bV) or violet-blue (vB) — and by saturation, from Light to Exceptional. Tanzanite is trichroic — it shows blue, violet and a flash of burgundy depending on the angle — and almost all of it is gently heated to bring out its blue: a standard, permanent treatment, always disclosed.

02Clarity

The finest stones are internally flawless (IF) — nothing to find even under 10× magnification. Most tanzanite is eye-clean (EC), so a stone free of visible inclusions is the expectation rather than the exception. The fewer and finer the inclusions, the higher the grade — and the more light the stone returns to your eye.

03Cut

Cut decides how much light comes back to you. Cushions and ovals hold colour; trillions and rounds add sparkle. Because the stone is trichroic, the cutter must choose which colour faces up — blue or violet — and will often give up weight to reach the finest hue.

This piece: Marquise

04Carat

Tanzanite’s colour deepens with size: stones above about five carats show the most saturated blues, and large, vividly coloured stones are the rarest of all. Weight alone never decides value — a smaller stone of exceptional colour outranks a larger, paler one.

This piece: 2.19 ct