Birthstone Guide: Opal for Those Born in October

With an iridescent radiance, the captivating opal is the birthstone for October. Here, Lily Faber FGA DGA EG, explores the history and properties of this fascinating gemstone.

Opals have been valued for millennia, even before Ancient Greek and Roman times. There are two main types of opal: precious and common. The precious variety shows that magical play-of-colour which is so highly sought-after and can capture the attention and imagination of anyone who lays eyes on one of these gemstones. The more common variety simply does not show this optical effect, but can come in a variety of colours from pink to green to blue to yellow. Another variety is known as fire opal, which is a transparent to translucent variety that is orange, red or yellow and sometimes displays play-of-colour, but often does not.


Precious Opal, Image Credit: Pat Daly

Believed by the Greeks to give one the power of prophecy and foresight, opals enjoyed a long period of favour. The Romans thought that opals represented purity and hope. Opals were regarded in high esteem until the 18th and 19th centuries when the perception changed and they were believed to be unlucky, causing misfortune and bringing harm to the wearer.


Common Opal, Image Credit Pat Daly

Prince Albert gave Queen Victoria the Oriental Circlet Tiara that featured 11 precious opals. These were later replaced with rubies by her granddaughter Queen Alexandra, who believed them unlucky.

 Opal with Striated Colour Patches. Image Credit: Pat Daly 

Prized precious opals were relatively rare prior to the 19th century, the best examples coming from present-day Slovakia. Today, there are many localities where opals can be found, but the best and most valuable ones were discovered in the late 19th century in Australia. Places of highly desirable opals include deposits in New South Wales called Lightning Ridge and White Cliffs. 

‘Synthetics’
There are many natural opals on the market, but there are also manmade ‘synthetic’ opals. First created by Pierre Gilson in 1974, these opals are very close to matching the physical and chemical structure of a natural opal. Synthetic is in quotations because it is not completely identical to its natural counterpart. It is essential that one must be able to distinguish between these manmade opals and the naturally forming ones when going to purchase an opal. This can be done with observation using a 10x loupe.

Natural opals with play-of-colour have irregular patches of rainbow hues that flash at many different levels within the stone as it is turned. The patches of colour are irregularly shaped and can be limited in the colours shown depending on the inner structure of the opal.


Synthetic Opal - Columnar Structure.
Image Credit, Gem-A, Pat Daly

‘Synthetic’ Gilson opals still display play-of-colour, but it can be much brighter and more consistently shaped and displayed throughout the stone than natural opals. Additionally, these patches of colour have a polygonal outline to them, giving a ‘lizard skin’ appearance. If cut as a cabochon, there will also be a columnar structure to the patches of colour on the side of the cabochon, which is completely unlike natural opals.

Care and Caution
Opals contain up to 30% water, which means that they are susceptible to drying out when exposed to heat. This can cause crazing, or cracking, that is irreversible. When storing your opals, always make sure that it is in a cooler temperature, preferably with a bit of moisture in the air (a small dish of water or cotton ball will do). Opals are also porous, and can be easily damaged by acids and chemicals such as detergents, perfumes and jewellery cleaner. Finally, opals are soft with a hardness of 6 on the Mohs scale. This makes them vulnerable to knocks, scuffs and abrasions, which means they are more suited for earring and necklace settings rather than rings in order to keep them safe while wearing. 

Opal Boulder, Image Credit: Gem-A

Today, opals are enjoying resurgence in popularity, despite the misgivings that they can bring back luck to those who wear them. For those born in October, opals can and should be considered a bit of gem magic to be enjoyed for their stunning play-of-colour that is unmatched by any other gemstone.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image: Precious Opal Matrix. Image Credit: Pat Daly. 


The Gems&Jewellery Autumn 2019 Issue Has Landed!

The Gems&Jewellery Autumn 2019 Issue Has Landed!

We are pleased to announce that the Autumn 2019 issue of Gems&Jewellery magazine is now available to Gem-A Members and students in print and online.

Read more


Understanding Spinel: The Alternative August Birthstone

Understanding Spinel: The Alternative August Birthstone

The varied hues of spinel have been admired for hundreds of years, but this gemstone only recently found its place on the list of ‘alternative birthstones’. Here, Lily Faber FGA DGA EG explores the alternative birthstone for the month of August and some of its synthetic counterparts.

Read more


Birthstone Guide: Peridot for Those Born in August

Birthstone Guide: Peridot for Those Born in August

Those born in August have vibrant green peridot as their birthstone. Lily Faber FGA DGA EG delves into this zesty gemstone to find out more about its physical properties and fascinating history.

Read more


5 Things to Consider Before Starting the Gemmology Foundation Course

5 Things to Consider Before Starting the Gemmology Foundation Course

Do you have a passion for diamonds, gemstones and the science of gemmology but have no idea where to start? Take a look at our guide to the Gem-A Gemmology Foundation and the things you should consider before taking this highly respected beginner’s gemmology course.

Read more


Understanding Tanzanite

Understanding Tanzanite

Our series of discovery into the Gem-A Gemstone & Mineral Collection continues with the brilliantly eye-catching tanzanite. Gem-A assistant gemmology tutor, Charles Bexfield FGA, delves into the history and unique properties of tanzanite and explores what makes this relatively new gemmological find so special. 

Read more


What Career Paths Can Trained Gemmologists Take?

What Career Paths Can Trained Gemmologists Take?

Are you fascinated by a career that utilises a gemmology skill set? Or perhaps you have completed your Gem-A Gemmology Diploma and want to know what’s next? Take a look at our guide to the opportunities open to gemmologists… you may be surprised!

Read more


Top 5 Most Famous Diamonds for Gemmologists

Top 5 Most Famous Diamonds for Gemmologists

Although all diamonds are special, there are some that are historically significant, spectacularly large and hugely important for gemmological research. Here, Rona Bierrum FGA DGA EG pinpoints the five diamonds that stand out from the crowd for gemmologists the world over. 

Read more


Gem-A's Gem Empathy Award Returns for 2019

Gem-A's Gem Empathy Award Returns for 2019

Gem-A is delighted to announce the return of the Gem Empathy Award for 2019, featuring a 12.9 carat precious coral cabochon as the prize stone. Find out more about this year's competition, and how to enter, here...

Read more


The History of Cardinal Mazarin's Extraordinary Diamond Collection

The History of Cardinal Mazarin's Extraordinary Diamond Collection

The Mazarin diamonds were a collection of 18 diamonds left to Louis XIV and the French Crown Jewels by Cardinal Jules Mazarin. Discovering the story of this group of diamonds, the man who collected them and what happened to them is like an incredible work of fiction. Charlotte Pittel FGA DGA takes us through their fascinating history.

Read more


The History of Queen Victoria's Sapphire and Diamond Coronet

The History of Queen Victoria's Sapphire and Diamond Coronet

Queen Victoria famously shared a love of fine jewels and coloured gemstones with her beloved husband, Prince Albert. In fact, one of her most prized possessions - a sapphire and diamond coronet - was designed and commissioned by Prince Albert in 1840. Here, we delve into the story behind this beautiful piece of history.

Read more


Birthstone Guide: Ruby for Those Born in July

Birthstone Guide: Ruby for Those Born in July

Those born in July can call the resplendent ruby their birthstone. To find out more about this historically significant and commercially successful gemstone, we asked Gem-A tutor Lily Faber FGA DGA EG to share her insights.

Read more


Exploring the Newest Jewelled Treasures of the V&A

Exploring the Newest Jewelled Treasures of the V&A

After 10 years and 4.2 million visitors, The Victoria & Albert Museum (V&A) has reopened its William and Judith Bollinger Gallery, home to its jewellery collection, after a three-month refurbishment with eighty new pieces joining the display.

Read more


Buying Guide: Saltwater versus Freshwater Pearls

Buying Guide: Saltwater versus Freshwater Pearls

Treasured the world over for their timeless elegance, lustre and iridescent, multi-tonal colours, pearls have for hundreds of years been a favourite of high-end jewellers and collectors alike. But how can you tell the difference between saltwater and freshwater pearls? And what should we look for when buying?

Read more