Opals are unique and are popularly known as the ‘Queen of gems’. They have mixed colours combined with brightness and sparkle. It is challenging to describe the colours of opals; all the colours of a rainbow are found in them. Nevertheless, some opals are colourless and transparent. Crystal opal is partially or entirely transparent and has a higher value than white opal stones. Since opal is amorphous, it doesn’t have a definite crystalline structure. Opal is found in Brazil, Ethiopia and Mexico. However, 95% of opal found in the world is from Australia. Highly-priced opals have diverse and intense colours.
There are two types of opals: precious opals and common opals. The significant difference between these two is that precious opals show a play of colours while common opals don’t display any colour. The play of colours is caused by the presence of silica in the opal stones. Opal stones are filled with numerous tiny silica spheres, and when light hits them, it bounces in different directions and angles, creating a sparkle of unique colours. The impurities cause the background colour in the opal stone.
What is the play of colours in opals?
The play of colour phenomenon is found in opals because the light rays entering the opal travel through the gaps between the silica spheres. As a result, the beams are forced to bend through the holes. Bending splits the light rays, and it forms different colours. The colours formed depend upon the size of the gap between the tiny spheres of silica. Smaller holes form blue and green colours, and more significant gaps create red, yellow and orange colours. Large gaps between the spheres are uncommon. Therefore, it leads to rare occurrences of red and orange opal stones.
Types of opals
White opal: White opals show colours against a white or transparent background.
Black opal: They are dark opals that display the colours against a dark background.
Fire opal: Fire opal stones show their colour against a bright red, yellow or orange background.
Crystal opal: These opal backgrounds range from transparent to semi-transparent.
Water opal: This opal is transparent and entirely colourless or has a minimum play of colour.
Boulder opal: The opal includes rock fragments as part of the finished gem.
Opals are found in various colours, but red is the most valuable and rarest colour. White opals are common and black opals are rare and expensive. They have a dark tone or are entirely black. Opals have patterns on them, and it is impossible to find two opals with the same design. Some of the most popular patterns are Harlequin, straw, floral, flagstone, pinfire and broad flash.
The value of an opal gemstone depends on its colours and patterns. Opals with brighter colours and patterns are more expensive than those with dull colours. However, the wholly colourless and transparent water opal has a high value. The factors that determine the value of opal are its colour, clarity, pattern, play-of-colour and brightness.
Why are opals expensive?
Opals are expensive because of their unique play-of-colour phenomenon. It is not found in any other gemstone. Each opal has a unique pattern and colour, and no two opals are similar. Opals of high value have large and bright sparkles of various colours. Additionally, they should have no cracks or inclusions. Black Australian opals are more expensive than diamonds.
Crystal opal has a transparent background. These opals produce a stunning lustre when faceted and are used to make high-quality jewellery like engagement rings. Opals delight people with their beauty and have a wealth of healing uses. Wearing opal jewellery makes people feel they are capturing the lightning through their jewellery.