The birthstone for October is Opal.
In ancient times, opal was symbolic of fidelity and reliability. It was believed to have therapeutic values for diseases of the eye.
The most valuable and the luckiest gemstone of all is the black opal. Black opal displays an array of vibrant rainbow colour effects with flashes of blue, green and red that reflect the light vibrantly. It really is like no other!
Opals are cabochon cut as faceting does not enhance the reflection of its colours. The majority of opals have a predominantly white background with the most valuable having a play of blue, green or pink colour.
What is opal and what is it made of?
Opal is formed from a solution of silicon dioxide and water over many centuries. It results in a gemstone like no other with an array of vibrant colours that flash in the light with an almost rainbow effect. The more intense or vibrant the display of colour, the more valuable the opal becomes.
This effect is created by the opal’s formation process which involves the composition of hydrated silica spheres. This interferes with the reflection of light in different ways. The arrangement of these spheres is responsible for all the fascinating colours.
In opals, colour really is everything. Some opals are very transparent and are classified as jelly, semi-jellyor water opals. One of the rarest is the harlequin opal which displays colour patterns resembling a checkerboard.
Where is opal found?
The very first opals are believed to have been discovered in Ethiopia thousands of years before Christ. Ethiopia still produces opals today, especially since opening up its gemstone industry in the 1990’s. Opals from this area occur in a wide range of colours. Ethiopian opals generally have a distinctive brown, red, or orange hue. However, yellow, white, and clear colours are also found.
Australia is considered to be the most famous of all countries for precious opals. Their discovery dates back to the late 19th century. Australia produce many different varieties of opal including white, crystal and boulder opal. However, it was the discovery of the vibrant and most colourful black opal in in the late 1800’s that really changed the gemstone world. Lightning Ridge is the home of this most beautiful and valuable type of opal.
How is opal formed?
As water runs through the earth, it picks up silica from sandstone, and carries this silica-rich solution into cracks and voids. As the water evaporates, it leaves behind a silica deposit. This cycle repeats over very long periods of time, and eventually opal is formed. The tightly packed spheres of silica in opal refract light passing through it, creating a play of colour that is fascinating and highly sought after in precious opal.
How can you tell if an opal is real?
The physical and optical properties of a created opal are almost identical to those of a natural opal. The main difference is that a created or synthetic opal has been impregnated with an extremely hard polymer resin which permanently binds the silica spheres together.
The resulting opal is 80-90% pure opal silica, exhibiting a play of colour and vibrancy that equals the most prized of all precious opals. The advantage is that its treatment results in a generally stronger and more stable gem than a natural opal, making it less vulnerable to heat, cracking or drying.
Although it takes several months to grow or culture a lab-created opal, they are still very affordable in comparison to a natural opal. Created opal is a form of solid opal and should not be confused with doublets, triplets, opalite, reconstituted opal or other imitations.
Different types of opal
There are many different types of opalavailable in the gemstone market today. These include white opals, black opals, blue opals, pink opals, fire opals, boulder opals, jelly opals, water opals, cultured or created opals, doublets and triplets to name but a few.
Below we outline some of the differences between the most important opals:
The most common form of opal has a white background, is translucent and usually displays opalescence. The finest specimens will show all the spectral colours. Although it is considered to be less valuable than black opal, it commands a high price and these opals are usually set in gold.
The black opal has a black body colour with very little opalescence, and they are considered to be the most desirable of all opals. The black background allows the blues, greens, oranges and reds to stand out in contrast to the dark background, supposedly making the play of colour that much more impressive. Normally set in gold these are very often beyond the reach of most!
These comprise of two parts glued together, the top is a slice of natural opal stuck to a dark opaque backing sometimes made of plastic or a natural stone material. In better quality examples ironstone is used to mimic the host rock of boulder opal. They are more affordable than solid opal but can still command quite a high price.
Synthetic opals have been created in a laboratory and have the same chemical composition, internal structure and appearance as natural opals. They are often referred to as lab-created opals, lab-grown opals, or ‘cultured’ opals to indicate their man-made origin. Many created opals look so much like natural opal that a trained gemmologist can have difficulty separating them from natural opals. Our own silver collections feature superb created blue opals and pink opals which rival some of the finest natural opals in terms of colour and appearance. They are of course far more affordable than natural opal and ideal for setting in 925 silver or in gold.
Mexican fire opal is a highly prized variety of Opal sourced exclusively from Mexico. It has a fiery body colour accompanied with, or sometimes without, a rainbow play of colour. Normally they are a transparent orange, red or yellow colour and may be faceted rather than cabochon cut.
Different opal colours
What colour are opals? It’s a hard question to answer as this is the only gemstone that can encompass a spectrum of so many different colours. There are several contributing factors to the unique rainbow of colours that an opal possesses. The internal structure has tiny organised silica spheres that bend the light and disperse it in this rainbow effect of incandescent colours. Whilst this diffraction of light creates a broad spectrum of vivid colours, some opals can appear to be more blue or green or pink or orange. Some of the most popular are blue opals and pink opals.
You can view our fascinating collection of blue opal jewellery here or our pink opals can be found here. You may also wish to browse our AAA grade created opals set in gold here. They all display a wonderful play of colour.
How to care for opals
Taking care of your opal jewellery is easy. All it requires is a little bit of common sense and some knowledge about opals.
Opal is a relatively soft gem, so it is important to treat all types of opal carefully in order to avoid damaging them. Remove your opal jewellery if there is a chance it will be scratched or broken i.e. working in the garden, playing sport or moving furniture etc.
Although water will not damage your opal, it is best to avoid getting it wet. Remove your opal jewellery when bathing, showering or swimming. Chlorine and sea water can cause damage or discolouration to both precious metals and gemstones. Constantly immersing jewellery in water can, in certain circumstances, compromise some gem settings (especially pearls and opals). Never immerse opals in oil as this will damage them.
Never allow anyone to clean opals in an ultrasonic cleaner, as the intense vibrations may cause damage. Opals may be wiped with a damp soft cloth and mild detergent. Avoid using jewellery dips or other chemical based cleaning solutions.
Try to avoid very high temperatures or low humidity extremes, such as boiling water or zero humidity bank vaults. Never leave opals lying in the sun. If you need to store your opals away for a period of time, simply place them in a padded cloth bag for protection and then store them.