Gemstones
Tanzanite Buying Guide
Tanzanite is a trichroic blue-violet gem found in only one place on Earth, usually heat-treated to achieve its signature colour.
A single source
Tanzanite is mined almost exclusively near Merelani, Tanzania, which makes supply geographically concentrated compared with most coloured gemstones.
Colour and treatment
Rough tanzanite is often brownish and is heat-treated — a widely accepted, stable, and typically undisclosed-as-exceptional treatment similar to sapphire heating — to bring out its vivid blue-violet colour. Untreated tanzanite is rare and may command a premium if documented.
Durability considerations
With a Mohs hardness of about 6.5–7, tanzanite is softer than sapphire and more prone to chipping, so it suits pendants and earrings better than rings worn daily, and should be set and stored carefully.
Buyer checklist
- ✓ Ask whether the stone is heat-treated (most are)
- ✓ Choose protective settings for ring use given moderate hardness
- ✓ Avoid ultrasonic cleaning to protect included or fractured stones
Verification tools & references
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