How to Assess an Opal’s Value?

Discover what makes an opal valuable – before you invest

Like any high-end purchase, you’ll want to ensure you’re investing in something that can hold its value over time. If it’s a gemstone or fine jewellery you’ve set your sights on, you can’t look past premium Australian opal – considered the best quality in the world.

The increasingly tight restrictions around opal mining have meant that there is less certainty around supply – creating an environment of surplus demand and limited supply. Due to the shortage of premium opals, it’s unlikely your opal will decrease in value in the foreseeable future.

There is an untouched uniqueness inherent in every opal – granting the owner a piece of exquisite nature, never to be repeated. With their uniqueness and scarcity comes a layer of complexity when it comes to assessing their true value. Solid opals have traditionally been considered the best investment. However, the popularity of opal doublets has risen over time due to their affordability and the elevation of competition.

The major difference between valuing an opal and a diamond is that there is no precise dollar to carat systemisation for opals. The information that informs an opal’s value is mainly trend-driven and circumstantial. If you’re considering investing in opal, it pays to be aware of the qualities that influence the value. Whether you’re making an investment or buying purely for aesthetic pleasure, learning more about these inimitable gemstones will only help solidify your decision making.

What makes an opal valuable?

The value of opal is measured on its rarity and a combination of characteristics. Natural solid opals are the most sought-after – they are polished directly out of opal rough with or (less often) without its host rock. In contrast, opal doublets contain a slice of opal fused to a common-opal or other backing.

You can read more about the different types of opals here.

Opals have an amorphous nature rather than crystal structure and contain tightly packed spheres of hydrated silica. The spheres are either packed with or without internal order. Common opal results from a lack of internal order and is significantly less valuable. Precious opal results from structured order and captivates with its magnetic play of colour. Its play of colour is determined by the way the light travels through the prism-like space between the internal spheres. You may experience hypnotic colour movement from the light bouncing between the spheres when you move a precious opal.

A general truism of the industry is the darker an opal’s body tone, the more value it holds. It’s assumed that a darker body tone gives more vibrance to the opal’s spectrum of colour, and that is why we frequently see black opal prized more highly than any other variety of opal. However, planning an investment based on body tone could lead you up the garden path. Instead, you may end up with an inferior opal only because its body tone is black N1. Body tone makes sense in monetary value only in combination with other factors such as colour play and variety, pattern and brightness. Some exceptionally coloured white opals make an excellent investment because they are bright and colourful and have a pleasing, harmonious pattern.

Opal body tone guide

The combinations of opal colours and patterns are endless. But a striking rainbow explosion usually attracts the most attention, as does a knockout display of two bright varieties in the same hue. Red against black is rarely seen and considered the most expensive and desirable colour combination, provided its play of colour is vibrant and bright. The brighter and more distinct the pattern, the greater its value.

Opal brightness guide

You may not be aware, but the direction of colour is also a crucial value gauge. Opal that shows vibrant colour from all directions is considered more valuable and versatile than a one-directional opal – with all other factors being equal. The best quality opal will shine with brilliance from every direction. A one-directional opal means the exhibition of colour can only be appreciated from a certain angle. A dead spot is when no colour is visible from a certain angle, which may lower the overall opal value.

Various opals pattern 

Opal brilliance refers to the brightness and clarity of the colours at play when the stone is being viewed face-up and ranges from brilliant, bright, subdued or dull. If the colours do not face you when you view the opal from the front, the value decreases.

Opal is typically cut in a cabochon shape. A cabochon with a high dome is more valuable than a flat stone, as it usually means that the thickness of the precious opal is greater.

Clarity is defined by the absence of disruptions to the opal’s colour play. You’ll want to avoid any opal with an inclusion or obvious imperfections, such as potch lines, sand, or a bad cut. The fewer inclusions, the better, unless they add subjective beauty in the form of a desirable or exciting pattern in the gem.

When you purchase opal, be sure to do so from an accredited supplier with a sound reputation. You’ll want to ensure that your opal comes with a Certificate of Authenticity to confirm the validity of the origin. At Opal Minded we also issue at request, Certificates of Valuation by our qualified gemmologists and valuers accredited with NCJV (principal valuers body in Australia) who undertake regular professional development and spend time at our opal mines in Jundah-Opalville, Queenlsand.

Many experienced jewellers and valuers shy away from handling Australian opals, as there is no agreed internationally nomenclature as yet, and experts rely on their experience and the breadth of their understanding of the state of the market to determine a stone’s value. Nevertheless, opals can make an excellent investment – just be sure of what you’re buying. The differentiating quality of precious opals is their play of colour, and the brighter – the better. Common opals have practically the same chemical composition, minus the magnificent play of colour. There are also synthetic, composed, and imitation opals, and opals of different origins and susceptibility to water. The market at the high end is small yet vibrant. Precious opal provides a one-of-a-kind value, and ultimately it comes down to how much one is prepared to spend to secure an outstanding piece of gemstone.