What Makes a Good Opal? Key Elements that Determine Value

In Pearl Jewellery
04 Jan 2016 | No Comments

It’s easy to become entranced by the brilliant colours of opals, but what determines the value of these precious gemstones? The value of an opal depends on a variety of factors, starting with type of opal, then if black will be body tone a well, then fire (brilliance), play of colour, pattern, cut, weight and if the case inclusions.

Let’s have a look at the role these factors play, so you’ll know what to consider when shopping for opal jewellery in Sydney or elsewhere around Australia.

Opal Type

Black Opals are most valuable as they are the rarest, then boulder, and last but not least, white opals. This is not related to beauty, but because of rarity. 90% of Australian opals are white, therefore the most available. There are as well doublets or triplets which include a fine slice of white opal. These are made using techniques whereby a slice of opal is attached to a backing and a clear piece of glass or plastic is glued to the top of the opal.

Body tone (for black Opal)

The body tone means the background colour of the opal. Black opal can start from completely black base through differerent shades of gray to almost white or crystal body tone. This helps to determine the value, because the darker the body tone, the more brilliantly other colours are displayed. For this reason, black opals are more valuable, than lighter opals as in body tones.

Play of colour

The play of colour refers to the magical quality of the opal to display an incredible array of rainbow colours. Basically, the most valuable opals display colour vibrantly, when viewed from all angles. When the play of colour crosses the entire spectrum, it’s considered rare and valuable. Prominent colours also increase the value, with red being the most desired.


When you view an opal face-up, look at the brightness and the clarity of the colours. Brilliance refers to how ‘brilliant’, subdued or dull the colours are and the value increases or decreases accordingly. This is one of the most important factors to determine value.


The pattern of an opal refers to the arrangement of the play of colour. There are many patterns, with valuable ones including harlequin, flagstone, ribbon, straw, Chinese writing and picture stones.


Inclusions are part of all natural gemstones. Inclusions when present in the face of the opal will that lower the value of the stone. Other types of inclusions are sand in or under the colour bar, grey lines, sections that may be lacking in colour and brown ironstone on the surface.

The weight and cut

Like diamonds, opals are also measured by carat weight. Craftsmen take into account the pattern, play of colour and brilliance when cutting opals. This may mean that opals are cut into irregular shapes in order to maximise the play of colour. Oval opals should be symmetrical with well-rounded dome shapes.

All opals are unique, and they come in a variety of shapes, sizes, and colours. These factors can all help you choose a good opal, but don’t forget that the most important thing is that the stone appeals to your personal taste!

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