November Birthstone: Topaz

Topaz is the original birthstone for November and the traditional gift for 4 years of marriage.

 

THE SCIENCE

Topaz is a silicate and is composed of Aluminium, Silica, Hydrofluric Acid and Iron. Topaz is allochromatic, which means that it is coloured by trace elements or defects in its crystal structure, rather than by elements of its basic chemistry. Chromium for example causes natural pink, red and violet-to-purple colours. While colour centres cause yellow, brown, and blue. However, if both Chromium and colour centres are present, the Topaz will be orange.

Topaz forms in the orthorhombic crystal system. This formation typically results in elongated rough crystals, with strong parallel groves, or striations parallel to their length. This formation results in cut stones often being long ovals or long pears to improve yield from the rough. If the rough is strongly coloured, the cutter will often choose the emerald cut to maximise colour and retain the most weight.

 

THE COLOUR

For centuries, Topaz was associated with the colour yellow. To the extent people assumed that all yellow stones were Topaz, and that all Topaz were yellow. Today they’re much better understood and in fact Topaz comes in a huge variety of natural colours, including red, pink, purple, yellow, orange and brown. There are also treated colours in shades of blue and green. The most common colour for Topaz is however colourless.

Topaz colours can be loosely broken down into 3 main value categories:

  1. Most Valuable: Pure red, Imperial (a stone with medium reddish orange to orange-red colour), Pink, and varieties with red predominant tones.
  2. Less Valuable: Yellow, orange, and brown.
  3. Colourless: Colourless or greenish gems that are converted by treatment into a huge variety of blues.

 

 

AROUND THE WORLD

While some Topaz crystals grow in metamorphic rocks (where stones change due to heat and pressure). Primary sources of gem-quality Topaz are pegmatites, where miners sometimes find huge crystals in cavities and pockets in the earth’s crust. Brazil for example produces some of the world’s most-prized Topaz colours including Red, Imperial, and richly coloured orange-yellow (sometimes referred to as Sherry Topaz).

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NATURAL OR TREATED

Colourless topaz is the most abundant form for Topaz to form naturally, and since the 1970’s it’s then been a standard process of subjecting these stones under highly controlled environment of radiation, followed by heat treatment to fix a colour, producing varying shades of blue.

The origin, colour, and specialised treatment of the starting material will depend on the resulting predictable uniform and repeatable colour of the final stones. Although most Blue Topaz is a result of this process, the colour is permanent, stable, and undetectable, however blues do occur naturally under exceptionally rare circumstances, but it’s impossible to tell the difference between them. Green stones natural or treated are not a stable colour for Topaz and will unfortunately diminish if subjected to strong daylight for periods of time. This unfortunately does not even have to be for long, so you will rarely find this colour due to its instability.

 

 

CARE IS NEEDED

Every Topaz crystal, whatever the colour or shape, has 1 undesirable feature that’s related to its atomic structure. In 1 direction, there are weaker bonds between the atoms (this is called cleavage) and in Topaz it runs parallel to the base of the original crystal growth. Due to this, cutters take special care to fashion finished gems at about 15 degrees to the original rough. This can help prevent damage to a certain extent in finished gems. Protective settings such a bezel or half bezel are often used for ring mounts, helping to protect the stone. If not, they are more often set as pendant or earring stones, which are less vulnerable to hard knocks or impacts during wear. You should avoid steam and ultrasonic cleaning your Topaz jewellery. Warm soapy water works best with a toothbrush for getting rid of dirt and grime in settings and from behind stones.

 

If your lucky enough to be born in November, you have quite a selection of different Topaz colours to choose from. Such as the rarer reds, oranges, and yellows to brown in smaller stones, or the abundance of cooler created colours from light/baby blues to deep and intense blues in more easily repeatable/matchable colours. Ideal for making matching sets of jewellery, these are often achievable in larger statement stones, but without a huge price ticket.

 

Don’t forget there is another birthstone for November! Stay tuned to find out more about the iconic and beautiful Citrine.