Overview
About Topaz
Topaz actually has an exceptionally wide colour range that, besides brown, includes various tones and saturations of blue, green, yellow, orange, red, pink, and purple. Colourless topaz is plentiful, and is often treated to give it a blue colour. Topaz is also pleochroic, meaning that the gem can show different colours in different crystal directions.
Birthstones & Anniversaries
Precious topaz is a birthstone for November and blue topaz is a birthstone for December. Blue topaz is the gem of the 4th anniversary and Imperial topaz is the gem of the 23rd anniversary.
1768
The royal court in Portugal celebrates the discovery of Imperial topaz in 1768.
271 kilos
A transparent topaz crystal discovered in Minas Gerais, Brazil weighs an astounding 596 pounds.
10 MeV
Irradiating colourless topaz with electrons at energy of 10 million electron volts creates a sky blue colour.
Facts
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Mineral:
Topaz
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Chemistry:
Al2(F,OH)2SiO4
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Colour:
Yellow, orange, brown, pink to red to purple red, blue, light green and colourless
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Refractive index:
1.619 to 1.627
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Birefringence:
0.008 to 0.010
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Specific gravity:
3.53
- Mohs hardness: 8
Treatments
There are a number of processes used to alter the colour or apparent clarity, or to improve the durability of gems.
Learn MoreSynthetics
Some gemstones have synthetic counterparts that have essentially the same chemical, physical and optical properties, but are grown by man in a laboratory.
Learn MoreImitations
Any gem can be imitated – sometimes by man-made materials or by natural materials chosen by man to impersonate a particular gem.
Learn More
Why We Love This Gemstone
Kilos
Topaz comes in some of the gem world’s largest crystals: the largest are kilos, not carats.
Slippery
Faceted topaz takes such a high polish it’s slightly slippery to the touch.
Pleochroic
Topaz is pleochroic, displaying different colours in different crystal directions.
Quality Factors
Topaz comes in a variety of colours from shades of blue to the rare reddish imperial colours.
Colour
The most valued topaz colours are orangey red to red. Blue gems are widely available.
Clarity
Topaz used in jewellery is typically eye clean with no visible inclusions.
Cut
Topaz crystals are usually columnar, and cut as oval or pear shapes to improve yield.
Carat Weight
Topaz often forms as large crystals. These can yield sizeable cut gems.
Topaz Quality Factors: The Comprehensive Guide
Research
Explore sources, gemmological research and the role of gems in history.
