Like many gemstones, tanzanite’s value is closely tied to its colour. The most desirable stones display a rich, velvety blue-violet tone, with minimal grey or brown undertones. Here’s a breakdown of the typical colour grading:
– Deep, saturated blue with strong violet overtones; excellent clarity. Very rare and highly valuable.
– Medium to deep blue with visible violet hues. Still striking and high-quality, but more accessible.
– Lighter blue with a more noticeable purple tint; often smaller in size or with some visible inclusions.
– Paler stones, often with noticeable inclusions or brownish undertones. These can still be beautiful, but are less valuable.
Pleochroism plays a role in grading too—well-cut tanzanite should show a dynamic range of colours depending on the angle it’s viewed from. A skilled lapidary will orient the stone during cutting to enhance its most vibrant face, often sacrificing carat weight in favour of exceptional colour.