Opal is the traditional birthstone for October and one of the most distinctive gemstones used in fine jewellery. Unlike gemstones known for a single defining colour, precious opals can display flashes of blue, green, yellow, orange and red that change as the stone moves.
This effect is known as play-of-colour and is created by the way light interacts with the microscopic structure inside the opal. The strength, range and pattern of these colours can have a significant effect on the stone’s rarity and value.
There are several varieties of opal, ranging from the familiar white opal to much rarer black opals and intensely coloured fire opals.
White Opal
White or light opal is what many people picture when they think of traditional opal jewellery.
These stones have a white, cream or pale body colour, often with flashes of different colours appearing across the surface. White opal is more commonly found than black opal, but fine examples can still be exceptionally beautiful and valuable, particularly when the play-of-colour is bright and visible across most of the stone.
Some white opals have a softer, almost milky appearance, while finer examples can show strong flashes of green, orange and red.
Fire Opal
Fire opal is quite different in appearance.
Rather than a pale background, fire opals have a naturally yellow, orange or red body colour and are generally transparent to translucent. They are particularly associated with Mexico and are sometimes referred to as Mexican fire opals.
Interestingly, a fire opal does not need to display play-of-colour. Some are valued primarily for the intensity and purity of their orange or red body colour, while rarer examples combine this rich colour with flashes of other spectral colours.
Their warmer colouring gives fire opal jewellery a completely different character from traditional white opal, particularly when set in yellow or rose gold.
Black Opal
Black opal is generally considered the rarest and most valuable major variety of opal.
The name refers to the stone's dark underlying body colour rather than an opal that is entirely black. This darker background creates a strong contrast against the play-of-colour, making flashes of green, blue, orange and red appear particularly vivid.
Fine black opals can therefore produce some of the most dramatic colour combinations found in any gemstone. All other quality factors being equal, the darker body colour and rarity of black opal mean it will usually command a higher value than a comparable white opal.
Why Is Red Opal So Valuable?
When assessing the play-of-colour within an opal, red is generally the rarest and most valuable colour.
Red is followed by orange, with greens and blues being more commonly seen. This does not mean that every opal containing red will automatically be more valuable than one displaying blue or green. Brightness, pattern, body colour and how much of the stone displays colour are all important.
A vivid blue-green opal, for example, can be more desirable than a stone containing only a small or dull flash of red.
However, when comparing opals of otherwise similar quality, strong red play-of-colour usually commands the greatest premium. A high-quality black opal displaying bright, dominant red colouring can sit amongst the most valuable examples.
What Makes an Opal Valuable?
There is no simple grading system for opals comparable to the 4Cs used for diamonds. Each stone needs to be considered individually.
Some of the most important factors include:
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Body colour, with darker black opals generally being rarer
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Brightness and intensity of the play-of-colour
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The colours present, particularly red and orange
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How evenly the colour is distributed across the stone
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The pattern created by the flashes of colour
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Transparency and clarity
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Size, condition and overall appearance
The best stones combine strong colour with brightness and an attractive pattern that remains visible from different viewing angles.
Choosing Opal Jewellery
Part of opal's appeal is that every stone is different. Two opals of the same size and type can have completely different patterns and colour combinations, so choosing one is often more personal than selecting a more uniformly graded gemstone.
Opals are also softer and more delicate than diamonds, sapphires or rubies, so they benefit from careful wear and storage. Rings in particular should be protected from knocks and abrasive surfaces.
For those born in October, opal offers considerably more choice than the traditional milky-white stone may suggest. From vivid Mexican fire opals to rare black opals filled with red and green flashes, it is one of the most varied gemstones available.
At Hatton Jewels, our collection of pre-owned, antique and vintage jewellery is constantly changing. If you are searching for a particular opal or would like to create a piece using a specific gemstone, our team can also help source stones and create a bespoke design through our Hatton Garden workshop.
