Everything You’ve Ever Wanted To Know About Different Opal Colours

The opal gemstone sets itself apart in the gem world with its completely one-of-a-kind display of ‘play-of-colour’. This gem, which appears as though it comes straight out of a fairytale, has set itself permanently in cultural memory as the October birthstone and Australia’s national gemstone. In this guide, we will answer the question of how opals come to look the way they do, describe the range of hues they come in, and discuss what drives up the prices of different coloured opals.

Opals are classified as a mineraloid rather than a mineral due to their lack of crystalline structure. They are separated into two classes: precious opal and common opal.

One of the most characteristic features of precious opals (alternatively called noble opals) is their exhibition of play-of-colour, or iridescence. This is when multiple colours seem to dance across and within the stone when turned against incoming light. Common opals, also called ‘potches’, do not display this phenomenon, rather appearing more milky with a distinct sheen which can be described as a glow from within called ‘opalescence’. If you’re wondering if an opal gemstone should be classified as precious or common, just check if it shows more than one colour. If it does, it’s a precious opal.

Chemically, opal stones are made up of hydrated silica. They form when water containing silica, a type of silicon dioxide, seeps into cracks between rocks in the depths of the Earth. (‘Hydrated’ simply refers to the presence of water.) 

As the water evaporates over millions of years, just the silica deposit is left behind. If you take a microscope to this leftover silica, you’ll see tightly packed silica spheres. It is the size and position of these spheres that produces its unique internal colour when light passes through them and diffracts in different directions.

In other words, it’s not the combination of chemical elements making up the stone that determine the colour of opals, as in the case of the various colours of emeralds. It’s the particular order and distance between the microscopic silica spheres that determines what colours the human eye perceives.

The stone of October babies can also show fluorescence of yellow, white, green, and blue; this on the other hand is attributed to trace amounts of uranium.

Opal gemstones are usually shaped into cabochons to best display these dazzling, naturally arising visual phenomenon.

All precious opals inherently display multiple colours, yet there is a ‘background’ or body tone that determines the main colour of both precious opals and potches. Here, we will introduce the most popular body tones of opals.

This is one of the most ubiquitous opal colours, along with grey and green, making it one of the lowest-priced opal stone colours. Precious white opals typically show fluorescent green, pink, red, and yellow play-of-colour, with potches showing a more muted, hazy colouration. In esoteric use, white opal is believed to absorb negative energy.

Opals with a grey body tone are also known as semi-black or simply dark opals. Grey opals offer a more opaque background for iridescence to show up, such that viewers can even see patterns in the different colours. Again, the particular play-of-colour of opals is due to the regularity of their internal structure, so the way they look varies according to the angle and intensity of light hitting them.

Pink opals are a variety of opal colour that exclusively occurs in common opals. That is, they tend to be highly opaque and don’t exhibit any ‘fire’. The hue of pink-coloured opal ranges from almost white to deep pink, edging on lilac. Their milky quality, with river-like tendrils of white bands, cause them to sometimes be confused with rose quartz. However, both can represent compassion, love, and healing.

Opal with a red body tone is among the rarest opal colours, along with black. Some red opals are called fire opals when they exhibit orange, yellow, or red with occasional green flashes. These range from fire engine orange-red to blood-red. Some opal gemstones exhibit a combination of black and red hues. This opal colour represents passion and fortune among gemstone hobbyists.

Opal stones exhibiting a blue background can be both common and noble. The common blue opal typically exhibits a pure baby blue or turquoise blue. Similar to pink potches, they also sometimes have meandering white bands. On the other hand, the noble blue opal ranges from royal blue to blue-black, with green, sky blue, and purple fire. Some believe blue opal has the power to reduce stress and represents balance between the sky and ocean.

On a rarity scale, orange-coloured opals are only less rare than red opals, making them fairly sought-after. Translucent orange opals can exhibit mesmerising combinations of green, blue, yellow, and purple fire. Opal stones containing a dominant orange body colour can also be called a fire opal. Thus, they share similar symbolic meanings with red opals: success and passion in all areas of life.

Opals with yellow hues can be potches or noble opals. They range from a pale canary yellow, to a dark mustard yellow, to a brighter, golden yellow. Yellow precious opals can exhibit green, blue, red, and orange flashes and are relatively rare compared to white opals. They can represent joy and confidence.

Another common opal variety, that is, showing no play-of-colour, is green opal. Opal stones with a green hue are typically made of silica that has mixed with a green mineral called nontronite. Green opals have a smaller range of saturations compared to the other different coloured opals; they are usually grass or lime green. In metaphysical circles, they are considered to be an energy cleansing stone.

Finally, black opals, especially those from Australia, are agreed by gemologists and jewellers to be the most expensive and desirable opal colour. It is the rarest hue that opals come in, and offers the ideal, undisturbed background for showing off the interplay of vibrant colours. Nearly all colours can appear in the play-of-colour of black-coloured opals, from red, yellow, and orange, to purple, blue, and green. 

Another characteristic that sets extremely dark opals apart is that they do actually contain trace elements of iron oxide and carbon that contribute to their multi-colouration. This rainbow-like quality lends it the special name of “Tears of the Gods”. In metaphysical practices, it offers emotional and bodily protection.

Inter-Pacific (the company over BIRON®) provides and sources the highest-quality lab-grown gemstones on the market. These ethical alternatives to mined stones can be made in a laboratory environment that exactly imitates the conditions under which gems form in underground environments. Besides offering lab-created opals in your desired colour and size at a significantly lower price than Earth opals, we also offer ethical emeralds, rubies, padparadschas, blue sapphires, diamonds, and alexandrite. Reach out to us to learn more.