What are synthetic and manmade gemstones anyway?

Have you ever wondered what a synthetic gemstone is… or a manmade one for that matter?

I am drawn to any sparkly stone and as a jeweller I appreciate the wide diversity of gems available and love finding ways to use them in my designs.  As a gemmologist I am fascinated by the man-made gemstones, how they are made and some of the stories behind the processes.

The gemmological definition of a synthetic gemstone is one that has the same physical, chemical and optical properties as its natural counterpart.  This means that the stone looks identical to its natural counterpart and has the same hardness, toughness and stability. A gemmologist can use various tests to identify a synthetic stone, although in some instances nowadays laboratory testing may be required for confirmation.

A gemstone’s properties are important because they not only allow gemmologists to identify the different varieties of gemstones, but they also give jewellers an indication of how to best work with and use a gemstone in their designs.  This could be knowing that malachite is a softer stone so will show signs of wear and tear in rings more quickly than sapphire, for example, which is a much harder gemstone.  It could be knowing that iolite and apatite are brittle gemstones which means they are liable to break or chip easily making them less suitable for the harder life of being set in a ring as well as the caution required when setting the stone

Stories from the laboratory…

The first synthetic gemstone was produced in the late 1800s by Auguste Verneuil who publicised his flame fusion process for synthesising rubies in 1902.  Despite the huge technical advances since then, I think it’s incredible that this process is still used today to grow synthetic spinel rubies and sapphires (including star stones).

I love discovering some of the stories behind the race to be the first to synthesise a particular gemstone.  They are full of amazing characters, such as Baltzar von Platen, the archetypal mad professor, described as “a genius maniac” who wanted to synthesise diamond.  In the late 1930’s he set up his laboratory in a decaying grand palace in Stockholm, built in the early 1600s by King Gustav Adolphus II for his mistress.  In 1942 von Platen started working with ASEA Sweden on his crazy invention with the intention of making “home-made Koh-i-noors” and nothing less would do!

ASEA were the first to successfully synthesise a diamond in 1953 (strangely enough, the experiment equipment had been set up in the outside toilets of the grand palace and ironically, this was just a year after von Platen had stopped working with the company).  Equally odd is that ASEA did not publish this monumental news until the American company General Electric (GE) announced their success in 1955.

There are stories of exploding experiments (just imagine the pressures they were trying to achieve – 70 kbar if you are interested, alongside temperatures of 1800°C), larger than life characters and fun little human stores such as the story of Chip, a little boy in America who, when he heard of GE’s success at growing diamonds, sent them a piece of coal in the post, asking if they could turn it into a diamond for him.  Some time later, a small parcel arrived for him from GE containing a little diamond crystal.

One of my favourites is another GE story where the scientists were looking for alternative carbon sources to use for their experiments to see just what materials they could grow diamonds from.  One of their colleagues was known to love snacking and always had food in his desk drawers so they stole a jar of his peanut butter… which produced little, green diamond crystals!

How are synthetic gemstones made?

Some synthetic gems are created by mimicking the conditions that the natural gems grew in, for example the High Pressure High Temperature (HPHT) process, or the hydrothermal process first used to grow synthetic emeralds in 1960.  

Other processes use different conditions, such as the Chemical Vapour Deposition (CVD) process for growing synthetic diamonds where atomic layers of carbon are laid down one at a time onto a tiny piece of diamond within a plasma.  I particularly like the Czochralski method, developed in 1916, which is used for growing synthetic sapphires, rubies and chrysoberyl.  Layers crystalise on a tiny piece of the gemstone material, growing into a bullet-shaped “boule” which is produced by slowly pulling it out of the chemical melt as it grows.  The crystal structure inside these boules is under stress so they are often split in half to reduce this and avoid the boule cracking.  Pulling the boule out of the melt in this growing process is why you will sometimes see pulled sapphires, rubies or alexandrite (the colour-change variety of chrysoberyl) for sale.

These synthetic gem materials are used for all sorts of things, such as diamond for drill bits and abrasives, water treatment filters, heat sinks in the electronics industry and even tweeters in high-end speakers or surgical scalpel blades!  If you own a watch, it may have sapphire crystal “glass” which is colourless synthetic corundum or tiny synthetic ruby jewels as bearings inside the mechanism.  

Currently you can find synthetic diamond, emerald, ruby, sapphire, spinel, transparent quartzes, such as amethyst, chrysoberyl and aquamarine gemstones available.  You may also see synthetic alexandrite, the amazing colour-change variety of chrysoberyl, but this might be synthetic colour-change sapphire as they are sometimes incorrectly sold as synthetic alexandrite.  

As with all areas, technology is moving fast and while Auguste Verneuil’s process from 1900 is still used to grow rubies, the technology for growing diamonds moves quickly.  From the early days in 1953 when the diamond crystals that were grown were definitely not gem quality, let’s move to 2014 when the largest gem-quality diamond grown using CVD was 3ct in size.  By 2018 this record had been broken by a 6ct diamond, grown using the same process.  I look forward to seeing how this develops further!  

It is not just the size of stones that are being grown which is astonishing, it is the increase in production of synthetic gem quality diamonds too.  In 2014 a few thousand carats in total were produced but by 2019 one factory in China alone produced 1.5 million carats.

So, what is the difference between a synthetic gemstone and a manmade one?  

While they are all made by man, synthetic stones share the properties of their natural counterpart while manmade stones do not - in fact, they might not even have a natural counterpart!

One of the manmade stones which doesn’t have a natural counterpart is cubic zirconia.  First produced in the mid-1970s, at room temperature this material’s atoms stack up into a monoclinic crystal structure but at temperatures over 2000°C its atoms move into a cubic crystal structure.  If a stabilizing element is added to the crucible while they are growing, the crystals will maintain their cubic crystal structure as they cool down to room temperature – hence the name Cubic Zirconia.  

I find it amazing that because these crystals need to be grown at such a high temperature (2750°C) there isn’t a material available that could survive being used as a crucible.  Instead, a crust of zirconia is kept cool on the outside and acts as a crucible for the crystals growing inside.  This is a process called skull melting and for some reason always makes me think of Indiana Jones and the crystal skull…  Something to note is that they are not related to zircon, which is a completely different, natural gemstone.  

As cubic zirconia is inexpensive to produce, the quality of cutting into faceted stones is usually poor with rounded facet edges, facets that don’t line up and even the odd extra facet!  The exception to this would be the Swarovski Zirconia which are reported to be made using the best quality cubic zirconia rough and cut with the same precision and attention to detail you would expect from a far more expensive stone.

Then there is synthetic moissanite which first appeared on the market in 1997.  Gemmologists refer to it as synthetic because tiny crystals have been found naturally so it does have a natural counterpart, but they are too tiny and rare to be used in jewellery.  This stone is almost as hard and resilient as a diamond and has a lot more fire (the flashes of rainbow colours caused by the dispersion of light). 

Some stones are marketed as “synthetic” but are not synthetic in the gemmological sense of the word and do not have the same properties as their natural counterpart.  This includes “synthetic” coral, lapis lazuli and turquoise which are made by sintering ceramic powders.  There are various types of “synthetic” opal on the market too, which are produced in a number of ways, but they do not share the same properties as a natural opal.

What other manmade gemstones might I see?

One that you will see for metal clay artists are nano gemstones.  These are made of a ceramic-glass material which is resilient to high temperatures making them great for firing in metal clay or casting in place with lost wax casting.  Being a ceramic-glass mix, they are harder than glass making them more resistant to scratching and abrasion while being worn.  Manmade glass is 6 on the Mohs’ scale of hardness while nano glass is 7½.    

Other manmade gemstones include goldstone (glass with tiny copper flecks), opalite (opalised glass), fordite (hardened layers of paint from the spray booths in Ford factories), surfite (layers of coloured resin from the manufacture of surfboards).  There are also those described as composites which have been created using some natural gem elements such as opal doublets with a thin layer of natural opal attached to a dark backing material or opal triplets which have the addition of a glass or quartz cap on top of the opal layer, giving the appearance of a single gemstone.

Then there are the “gemstones” deliberately made to deceive, such as Rainbow Calcilica. I remember first hearing about this stone in the early 2000s and thinking it looked colourful and sounded pretty exotic. It was described as a natural stone found in a mine near Chihuahua, Mexico but no one was ever allowed to visit the mine to verify this and the photographs of the mine had an unreal look to them... Intrigue and mystery and much discussion in the trade! In 2002 the Swiss Gemmological Institute (SSEF) analysed samples of the material and reported that it is pulverised carbonate rock mixed with at least two artists' pigments and stabilised with a polymer - so, manmade not natural.

It is also important to remember that glass has long been used to imitate many coloured gemstones and that even plastic is used to imitate amber, opal and mother of pearl.  This is not a problem as long as you, as the buyer and potentially the seller of the stone in a piece of jewellery, are aware of this fact and share the information.

Why are synthetic gemstones so useful for metal clay artists and jewellers?

There are a couple of important factors here – the first is the temperatures the gemstones were grown or manufactured at, the second is that they don’t have some of the vulnerabilities natural stones have such as liquid-filled inclusions or surface-reaching fractures.

Neither firing in a kiln or with a torch will approach the temperatures synthetic gems or cubic zirconia were grown in.  Having said that, a stone-set piece of jewellery should be slowly heated and allowed to slowly cool back to room temperature (never quench in water or pickle!) to avoid thermally shocking the stone which would break even these manufactured stones.

Heat is used as a treatment to improve or alter the colour of some natural gemstones which is why some manmade gemstones also change colour if they are fired – in a way, you are heat treating them!

Does it matter if my stone is natural, synthetic or manmade? 

This may become an issue when you are working with a gemstone or selling a piece of jewellery you have made.  Knowing exactly what gemstone you are working with will help to reduce the risk of damaging a stone.  For example, we know that goldstone is in fact glass with tiny copper inclusions – while we know that glass can be fired in place with some of the lower temperature firing metal clays, goldstone may lose its lustre and become dull and dark.  We also know that cubic zirconia can be fired in place in metal clay but a faceted piece of glass wouldn’t survive higher firing temperatures and could potentially destroy a piece of jewellery you have spent a considerable amount of time working on.

If you were going to torch fire what you thought was a synthetic ruby in place in your metal clay design, but it was actually a natural ruby which had been treated, the likelihood is that the stone would be destroyed.  This is because the natural stone may have fractures or inclusions which may shatter a stone apart when heated (or even have glass filling in fractures which could melt and destroy the stone…).  A synthetic ruby will have few if any inclusions or fractures and be far more resilient when being heated.

Turning it the other way around, it would be difficult if you sold a piece of jewellery which you believed contained a natural sapphire when in fact it was a synthetic sapphire or even a synthetic spinel (or a kyanite or a piece of blue glass…).  This affects both the price and your customer.  A natural sapphire is likely to be far more valuable than any of these similar looking stones and your piece of jewellery would have been priced to reflect the value of a sapphire.  You would not be happy if you had paid a gem dealer for a sapphire and neither would your customer when you later sold your work.  

Gemmologists are working to improve the gem industry and promote full disclosure of the true nature of gemstones offered for sale, whether they are natural, synthetic or treated.  To help protect both themselves and their customers, it makes sense for jewellers to buy gemstones from dealers that they know and trust, or those that have been personally recommended to them.  

I have a box of “buyer beware gemstones” that I take with me to show students attending my gemmology and gemstone days because I am passionate about helping consumers become better informed about this.  Sometimes the dealer has been misinformed by their supplier but sometimes they most definitely have not, and it is obvious that they are misleading their customers.  I am sorry to say I love trawling the internet looking for these horrors to add to the teaching kit… unless they are charging a ridiculous price of course!

So, as a jeweller, what does all this information really come down to?

If you like the look of a stone and are confident in its identity – buy it and enjoy it, regardless of what it is!  Knowing its identity will allow you to choose the best way to work with the stone without damaging it, as well as knowing how to look after the stone as you or your customer wear it and enjoy it.

If you like the look of a gemstone but are not convinced of its advertised identity, consider the price being asked – if it seems too good to be true it probably is!  If you are happy with the price and happy to risk it, think about setting the stone after your piece of jewellery has been finished so that you are not exposing the stone to possible damage.  If you are then selling the piece of jewellery, be honest with your customer and explain that, while you are not sure of its identity, you fell in love with it and hope that they do too!  They will appreciate your honesty and professionalism.