Imperial Topaz, courtesy of Sotheby's
Topaz
Topaz
Hard and brilliant, with a perfect cleavage that demands respect.
- Mohs hardness
- 8
- Crystal system
- Orthorhombic
- Composition
- Al₂SiO₄(F,OH)₂
- Colours
- Imperial (orange-pink), Sherry, Blue (sky/Swiss/London)
- Origins
- Brazil (Ouro Preto - imperial), Pakistan, Russia
- Birthstone
- November (imperial), December (blue)
Imperial topaz - the natural pinkish-orange material from Ouro Preto, Brazil - is the most valued variety. Most commercial blue topaz starts colourless and is irradiated then heated to produce sky, Swiss and London blue tones.
Topaz's perfect basal cleavage means setters and wearers must avoid sharp impacts despite its high Mohs hardness.
Treatments
What to know
- Irradiation + heat - produces blue topaz from colourless
- Surface coatings - produce 'mystic' iridescent topaz (less durable)
Care & handling
How to wear it
- Avoid ultrasonic and steam due to cleavage
- Warm soapy water only
Jewellery use
Setting the gemstone
Pendants, earrings and rings in protective settings.