Opal: The October Birthstone

What Is An Opal?

Opal is a form of silica, chemically similar to quartz but containing water within the mineral structure. 

Precious opal generally contains between 6 – 10% water and consists of microscopic silica spheres arranged in a regular pattern. It’s these silica spheres that determine the colour of the opal - large spheres create reds and small spheres go through the spectrum of colours with the smallest creating blues.

Australia produces over 90% of the world’s precious opal with some of the most famous mining areas including Coober Pedy, Lightning Ridge, Yowah, Quilpie and Koroit. Other countries such as the US, Mexico, Ethiopia and Peru (amongst others) produce precious opal and fancy varieties of common opal.

SHOP OPALS

Opal Facts

Colour: Opal comes in an array of colours from white, grey, blue, green and pinky orange - depending on its 'group'.

Appearance: Transparent and opaque.

Rarity: So far opal is easily obtained, however, there are certain variants that are rare and whilst there is no standardised or set method for valuing opals (as each one is so unique), there are a number of elements that make a boulder opal higher quality than others for example, the play of colour, brilliance and pattern.

Mohs Scale Hardness: 5 - 6

Sourced: Australia, Mexico, Peru, United States and South America.

Healing: Opal is thought to strengthen memory and therefore help treat Parkinson's disease. It is also thought to fight infections and fevers as well as purify the blood and kidneys as well as help to regulate insulin, ease childbirth and alleviate PMS.

Formation and History: Opal falls under two main varieties: precious opal or the 'opalescent opal' and the common (potch) opal. Their physical properties vary considerably and there are many varieties of each type. 

There are two groups of precious opals - those with a white or light basic colour, known as white or milky opals, and the rarer black opals - these are dark grey, dark blue or grey black - deep black is considered rare. 

Precious opal displays beautiful flashes of colour, whereas common or potch opal displays no iridescent colour and is often opaque (however it can still be very attractive). 

In ancient Rome, opal symbolised love and hope. The Romans gave it the name opalus, meaning “precious stone.” Opal has been a popular, symbolic stone for many centuries. Arabic legends say it falls from the heavens in flashes of lightning. 

The ancient Greeks believed opals were a gift of prophecy protected against disease. Europeans have long believed the gem is a symbol of hope, purity, and truth.

Meta-Physical Properties: The opal is known to stimulate originality and dynamic creativity, as well as aid in accessing and expressing one's true self. The Crystal Bible (by Judy Hall) explains that the opal is absorbent and reflective - picking up thoughts and feelings, amplifying them and returning them to the source - teaching us that what you put out comes back. Opal amplifies traits and brings characteristics to the surface for transformation. Enhancing self worth and helping you to understand your full potential.

Opal is believed to encourage spontaneity and it is said that the gemstone is associated with love and passion, helping you to release your inhibitions.

How To Identify Synthetic & Imitation Opals

Synthetic opals (such as Gilson Opals) are made from the same chemical composition as natural opals (hydrated silicon dioxide), so they have a similar structure to that of a precious opal, but they are produced in a laboratory.

Synthetic stones can look like genuine opal, but often show brighter colours with colour patches being much larger than those found in natural opal. The colour grain boundaries are generally highly irregular in synthetic opal and within each colour grain there are numerous sub-grains producing a distinctive snakeskin pattern.

They also generally show a more ordered array of colours since artificial material doesn’t duplicate the intricate pattern of natural opal.

Imitation opal is a non-opaline material (so not the same chemical composition as natural opal) often set in clear plastic or epoxy resin. These are much easier to distinguish from natural opal as they usually have a pearly opalescence rather than a play of colour, with opalite probably being the best know imitation opal.

Opalite: There are two very different stones on the market called opalite. The lesser known is a variety of common opal which contains moss like inclusions, whereas the other (and the far better known) is a man-made product made of glass which is often miss-sold as opal or even moonstone. We have seen opalite being miss-sold as a genuine gemstone far too often, and sometimes where the seller is genuinely unaware that they are incorrect (perhaps where they themselves bought it as a 'genuine gemstone') so please beware and always buy from a trusted supplier.

Opal Myths: Are Opals Really Bad Luck?

Opals were once believed to be bad luck (some people still believe this to be the case!), but you can date this rumour back to a number of possible causes.

One, is that Sir Walter Scott published a novel in the mid 1800’s called Anne of Geierstein, where he used an opal to reflect the changing fortunes of the heroine. Book critics thought that the opal had an evil influence due to some of the heroine’s misfortunes (although this was never the intention of the author) – a myth that dramatically reduced the value of opal at the time!

It is also said that the rumour of opals being bad luck was started by diamond merchants in the mid 19th and early 20th centuries once they realised that opal was a serious threat to the diamond trade. Opal was being commercially mined and was increasing in popularity, however, the ‘bad luck’ myth soon damaged the reputation of opal.

Another myth is that opal is a fragile gemstone and so it’s bad luck to wear. At 5.5 – 6 on the Mohs Scale it is a similar hardness to turquoise, lapis lazuli and labradorite and is harder than malachite and fluorite. So yes, we wouldn’t recommend wearing an opal when gardening, playing sports or similar, but they’re actually not as fragile as some people believe.

Remember that in Australia they say the only bad luck about opal is not owning one!

Ethiopian Opal

Ethiopian opal first came on to the market in 1993, although there are records of it being used by early cavemen in Kenya. It was rediscovered in the early 90s in the Shewa Province of Ethiopia. A new deposit near the Wollo Province was later discovered in 2008 and has been producing opals of a higher quality. Ethiopian opal comes in a variety of colours, from white, yellow and orange to dark red and chocolate brown, which varies between translucent and opaque. The play of colour is the same as other opals, coming in every colour of the spectrum.

Ethiopian opal is hydrophane opal, the term comes from the Greek words meaning 'water loving' as the stone is porous and will absorb water which can change the stone from opaque or semi-translucent to transparent - this can sometimes highlight the colour play or if it becomes completely transparent no colour play will show at all. This behaviour is typical of the stone and you may notice the stone looks different in different weather, depending if the atmosphere is very damp or dry.

The good news is that tests by GIA and others have shown that opal from the Welo province in Ethiopia will revert back to its original state, once dried, with no adverse reaction such as cracking. It is part of the stones nature to change in appearance and absorb water but you may wish to take precautions to keep your Ethiopian opal jewellery out of water when washing or doing household chores to help to prevent changes to the stone or it absorbing perfume, cream, soap or cleaning products which could stain or change their colour.

Boulder Opal

The term ‘boulder opal’ covers three sub categories of opal that are all formed in sandstone and ironstone: The most common is Boulder Matrix, which comes from the fields of Yowah and Koroit in the South West of the state where beautiful ‘pictures’ are created between the matrix (the host rock) and the opal that entwines around it creating little works of art.

Then there is what is termed as Boulder Opal, which comes from a seam of coloured opal in the rock which is cut and polished to reveal opal with colours that flash and move together in one band of colour or colours

The rarest of all three is Opalised Wood (this is the cutter's favourite type of boulder opal). This forms in roots of wood where the matter decomposes leaving gaps where the opal, a combination of silica and water, trickles into it. Over a process that takes millions of years, unique patterns are formed between the opal and the fossilised wood.

Solid White Opal

Solid opal is exactly that; it consists entirely of opal material without any other host rock and can be a combination of both precious opal and common opal. White opal is the most commonly available type of opal and is therefore less valuable than boulder opal or black opal. However, it is still extremely beautiful and can exhibit all the colours in the spectrum with some stones fetching over £100 per carat. 

Fire Opal

Fire opal is translucent and ranges in colour from bright red, orange, yellow to transparent. As it has no play of colour it is technically a common opal, however, with its strong colours it can be a stunning and valuable variety of opal. 

Black Opal

Black opal is predominantly mined at Lightning Ridge in New South Wales, Australia, which is world-famous for its black opals. More has been mined there than at any other location in the world.

The name black opal refers to the distinctive black ‘background colour’ or ‘body tone’ and not the play of colour present in the opal. Black opal often has a natural layer of potch left on the back of the stone which can give the stone extra darkness and therefore a more vibrant play of colour - this gives them their higher value. Because of their vibrancy of colour, black opal is more valuable than clear opal or white opal.

Semi-black opals are also known as dark opal or grey opal and cover any opal which is too dark to be classed as a white opal, but aren’t dark enough to be a black opal, these mostly come from Lightning Ridge.

Dendrite Opal

Dendrite opals have no fire but the milky white material is punctuated by delicate natural fern/tree-like black and grey markings of manganese oxides.

The stones are often reminiscent of a wintry forest. The complex patterns in contrasting black and white are quite amazing and each very unique in their patterns.

Pink Opals

Pink opals are one of the rarer colours of the opal and range in hues from blush pink to bubblegum pink, with the Peruvian pink opal being the most saturated pink opal. It's a natural type of common opal, usually containing palygorskite and chalcedony.

If you're after a birthstone gift, why not opt for pretty pink as a sweet alternative. Pink opal jewellery has also been used in history for romantic relationships, representing love, protection and healing.

Peruvian Opal

Peruvian blue opal is relatively rare and is only found in the Andes mountains near San Patricio, Peru. It is the national stone of Peru.

Peruvian opal is a translucent stone with colour similar to the beautiful tropical Caribbean Sea. Depending on how the stone is cut it can be clear, scenic (showing varying degrees of colour) or dendritic which has black fern like inclusions.

Unfortunately, in recent years dyed stones have been sold by dealers as Peruvian blue opal. Dyed stones are quite common and sell very cheaply at gem shows and on internet auctions. You can sometimes tell if a stone is dyed if the blue colour is uneven.

Opal Doublets

Opal doublets consist of a very thin slice of precious opal that has been cemented on top of either common (potch) opal or another host rock. As some opal has very thin but brilliant layers of fire, this can give doublets extremely beautiful colour.

Due to the nature of the doublets, care must be taken when setting them as the edges can be vulnerable to chipping and you should avoid prolonged exposure to water as this will eventually cause ‘lifting’ between the layers.

Opal Triplets

Opal triplets are similar to opal doublets, as they are made up of layers. As the name suggests they have three layers, a black stone backing, a slice of opal in the middle and a domed piece of crystal quartz or glass on the top. Our opal triplets are capped with natural quartz (making them more hard-wearing than opal doublets) and much better quality than those capped with glass that can be prone to chipping. You should avoid prolonged exposure to water as this can eventually cause ‘lifting’ between the layers.