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Composite gemstones: Lead glass filled rubies


If you read about my field gemmology trip with Vincent Pardieu in April 2017, you’ll know how I learned about the existence of composite gemstones and lead glass filled rubies.

Lead glass filled rubies entered the market in 2004, but since many people (especially hobbyists and tourist collectors) are still unaware of their presence, I wrote about them in ‘Buying Gemstones and Jewellery in Thailand.’  After all, Thailand is a world hub for gemstone treatment and continues to be where most of the lead glass filled rubies (also known as ‘composite rubies’) are manufactured these days.

Composite gemstones rubies |

So, for those of you who want to know more about lead glass filled rubies, here’s an excerpt from the book:


In the grand scheme of things, 95% of all gemstones sold have been treated in some way. With rubies and sapphires, the figure is closer to 99%. Heat treatment is the norm and something that you shouldn’t usually worry about — unless you are intending to buy a natural, unheated gemstone, in which case you would be investing thousands of pounds and would expect it to come with a lab report. Be on your guard if someone tries to sell you a good-looking, ‘untreated’ stone!

Gemstone Detective |

Remember: if it looks too good to be true, it almost certainly is.

Thailand is considered a world leader in gemstone treatment techniques, which can work both to the buyer’s advantage or against it.

Heat treatment simply enhances a gemstone’s natural beauty and clarity. Thailand is famous for the skill of its craftspeople, who have over the past 30 years or so developed sophisticated variations on the traditional art of heating gemstones to improve their colour.

Unless you’re looking to spend a vast amount of money, your primary aim should be to make sure the gemstone you are about to buy is genuine and not a piece of cheap fakery.

This said, there is a huge difference between rubies and sapphires that have been fissure treated in the traditional way and ‘composite’ gemstones, which are formed in the lab using a fairly recent technique. The appearance of traditionally fissure-treated rubies and sapphires is enhanced by using miniscule amounts of glass to fill any tiny inclusions on the surface of the stone. Composite gems are formed from lower quality corundum, which is acid treated to remove all the inclusions. The holes left behind are then filled with leaded glass. Leaded glass is very clear, but is even softer than ordinary glass and this means that composite gems are significantly less tough than their traditionally fissure-treated cousins.

Not only is the leaded glass in composite gems less tough than ordinary glass, its presence makes analysis of the corundum itself much more difficult. This means that it is harder for a grading

laboratory to determine the quality and weight of the original stone. Some composite stones are more than 40% glass! Furthermore, a composite ruby or sapphire whose corundum has many or deep fractures is difficult to distinguish from one whose corundum has only minor fractures. The former is much less durable than the latter.

Composite gemstones lead glass rubies |

Buying a composite gem is just fine if you know what you’re buying and have paid an appropriate price for it. The problems come when dealers knowingly — or unknowingly — try to sell you a composite ruby as a traditionally fissure-treated stone. Not only will you be paying much more than the stone is worth, but your piece of jewellery will be far more susceptible to damage and degradation.

If you decide to get the gem re-set or professionally cleaned, if you need a ring re-sized, or even if you wear your jewellery while cleaning or cooking, a composite ruby is likely to be damaged irreparably.

Composite gemstones are easy to identify if you can use a jeweller’s loupe — a small magnifying eyepiece used to examine gems. At 10x magnification under a strong light you should be able to see gas bubbles in the glass, heavy fracturing and an effect that looks like streaks of a different colour flashing across the stone.

Kim Rix GG GIA

Author of Gemstone Detective

Be sure | Be smart | Buy with confidence

My Field Gemmology Experience


I met Vincent Pardieu in July 2016 when he was the guest speaker at our London GIA alumni event.   At that time he was Head of Field Gemmology at the GIA in Bangkok, Thailand.  His fascinating talk on collecting rubies in Mozambique had me gripped from the start—ruby is my favourite gemstone. 

Vincent Pardieu at GIA |
Vincent Pardieu speaking at the GIA alumni event on 1st August, 2016

Before he had even finished his talk, I had decided that my future with gemstones wouldn’t be in a laboratory, but out in the field, where I could nurture my love for gemstones while exploring the world.

After Vincent’s talk, drinks were served, and networking started.  I boldly approached him, introduced myself and expressed my wish to travel with him.  Vincent explained that he only travels with people he knows well and can’t risk having someone who is a liability or slows up the team.  Some of his trips might involve 16-hour treks through dense jungles so stamina is of huge importance.  He made it very clear that he is not a tour guide and has no interest in being so again.  His trips have a very clear purpose—to build a reference collection for the GIA to determine a gemstone’s origin. Point taken.

Three lunch meetings later in Bangkok and London, Vincent invited me to join him to photograph his next expedition in Thailand.  My passion and persistence had paid off.

Little did I know that I would find myself back at the very same Khao Ploy Waen sapphire mines I had visited at the end of 2016.  After spending 7 months in a classroom studying gemmology full time, I had been desperate to go travelling again, so had treated myself to a celebratory field gemmology trip to Chanthaburi.  What a happy coincidence!

So, in April 2017, I flew to Bangkok to join Vincent.  I was expecting to head to Chanthaburi the following day, but received news that the trip was delayed.  Vincent had been caught up in an ongoing media frenzy relating to a sapphire rush in north-east Madagascar six months earlier.  It was a troubling time for Vincent and for the gem industry as a whole.

I spent a tense 3 days waiting in my hotel.  Thankfully, Vincent was eventually able to give us the green light, and off we headed in the minibus to Chanthaburi.  For the first day or two, the media handling of the sapphire rush continued to be the topic of heated conversation.

Field Gemmology in Thailand |
Vincent Pardeiu talking with the young gemmologists about the importance of research

The field trip was incredibly interesting and I thoroughly enjoyed being part of Vincent’s team.  It’s always more fun when you have people to share the experience with.  I learned a lot from Vincent, including one very strange incident which taught me some important lessons…

Vincent stopped me in the street and to my surprise put a gemstone in my hand.

“What is it?” he asked.  I looked at it.

“At first glance it looks like a very nice star ruby,” I replied.  He told me to look again more closely.  I took my loupe out and examined it more closely.  I wasn’t sure what he was getting at.  He told me to look for the gas bubbles as it was a lead-glass filled ruby. I explained that I had never actually seen one before (or, indeed, known of their existence) at which point Vincent berated me for not looking where I was standing whilst I was examining it. I was speechless, given that he’d been the one to stop me in the street and give it to me. I had no idea where he had got it from.  He took it back, turned around and gave it back to an elderly man who was no doubt trying to find a naïve tourist to hoodwink. I felt even more stupid because I had obviously fallen for it!  I kept my eyes a bit wider open from then on.

Field Gemmology expedition 2016 |
Field Gemmology – counting the mines across Khao Ploy Waen, Thailand 2016.
Field Gemmology with Vincent Pardieu |
Field Gemmology – learning about culture around Chanthaburi town in Thailand 2016
Khuk Khi Kai Chicken Pooh Prison |
Talking about history, inside Khuk Khi Kai Chicken Pooh Prison in Thailand
Young gemmologists learning field gemmology |
Talking about Field Gemmology at Khao Ploy Waen mine with Vincent Pardieu
Field Gemmology Boat trip with drone camera |
Boat trip to Lion Island – setting up the drone camera
Enjoying Thai coconuts |
Enjoying the Thai hospitality – shade and refreshing coconuts!
Vincent Pardiue with Justin K Prim talking field gemmology |
Making a video at the mine in Chanthaburi – Vincent Pardieu talking with Justin K Prim
Field Gemmology expedition 2016 |
End of another day learning about Field Gemmology with Vincent Pardieu, Thailand 2016

Probably the most important lesson Vincent taught us all about field gemmology was ‘always expect the unexpected.’  That three-day delay was unexpected and it was certainly a surprise when out of nowhere he popped a beautiful 30 carat lead-glass filled star ruby into my hand!

It’s a lesson I have since applied to every single trip I have made while writing my Gemstone Detective series. Older and wiser, I automatically expect the unexpected. In today’s day and age, it’s a good life lesson to learn.

After the trip, Vincent Pardieu published a video of our field gemmology trip, which I’m pleased to be able to share with you.

Kim Rix GG GIA

Gemstone Detective

Be sure. Be smart. Buy with confidence

September’s birthstone: Sapphire


September’s birthstone is sapphire.  If you’re a September baby, then lucky you – regal and stylish, there’s a variety of this gorgeous gemstone to suit everyone.

September's birthstone sapphire |

The word sapphire comes from the ancient Greek sappheiros meaning ‘blue’, which itself comes from a Hebrew word meaning ‘precious gem’ and possibly from a Sanskrit word meaning ‘dark coloured’. 

It’s probably the case that when someone says ‘sapphire’, you think of a deep blue gemstone, but did you know that sapphires occur in many different colours?   With blue, pink, green, yellow, orange, purple, black and even colourless to choose from, you won’t be stuck for a sapphire to match your favourite outfit.

September’s birthstone doesn’t come in red, though, and that’s because red sapphires are actually…rubies!  Both sapphire and ruby are varieties of the mineral corundum and all corundum’s various colours are caused by different chemical elements within it.  For example, titanium and iron in the corundum give rise to an intense blue sapphire, and trace amounts of vanadium produce sapphires of a purple hue.

September's birthstone sapphire |

After blue sapphires, the padparadscha is the most prized ‘fancy’ sapphire.  Padparadscha means ‘lotus flower’ in Sinhalese, one of the native languages of Sri Lanka and was named because the gem has the same gorgeous salmon-pink colour of the blossom. 

Corundum is the second hardest mineral after diamond—9 on the Mohs scale of hardness—which makes it a great choice of gemstone to wear in rings that are prone to knocks and scratches

If you’ve chosen sapphire for an engagement ring, you’re in famous company.  The Duchess of Cambridge, Kate Middleton, wears the engagement ring that famously once belonged to Diana, Princess of Wales—a 12-carat, cornflower-blue sapphire surrounded by diamonds. Princess Eugenie’s engagement ring too, is a sapphire – a stunning, peach-coloured padparadscha.

Another reason to slip a sapphire on your beloved’s finger is that sapphire symbolises fidelity and sincerity when used in an engagement ring!

Star sapphire |

Sapphire can occur as a phenomenal gemstone—a gemstone that displays certain optical effects. A sapphire with asterism (a so-called ‘star sapphire’) will seem to have a six-rayed star floating across the surface of the stone; a colour-change sapphire will appear to turn another colour in different lighting conditions and a bi-coloured or ‘parti’ sapphire (typically found in Australia) displays two colours within the stone regardless of the light source.   

September's birthstone |

Not only September’s birthstone, sapphire is also the traditional gift for a 45th wedding anniversary and a 65th jubilee. 

Some practitioners of alternative therapies use sapphire to promote the immune system and impart clarity and wisdom to their patients.  Whether or not you believe in the healing properties of gemstones, September’s birthstone certainly makes it a wise choice!

Kim Rix, GG (GIA)

Gemstone Detective

Be sure. Be smart. Buy with confidence

Who is author Kim Rix – Part 3


I hope you were able to find a few minutes to read Who is the Author – Parts 1 & 2. This is the final Who is the Author Q&A blog post.

What is the biggest mistake people make when buying a gemstone that you tackle in the books?

The biggest mistake I think people make is being too trusting.  One thing that I have learned through my travels is that not many people working in the gem trade have real knowledge about what they’re selling.  They might talk the talk – but how much do they really know about gemstones?  You have to be so careful about who you buy from!

Unfortunately, it often comes down to survival.  Competition is cut throat, there are bills to pay and families to feed.  It’s a dog eat dog world out there and many people are willing to be dishonest to make money.

But that’s why it’s so important to take care and buy from people who can advise you properly – people with real knowledge and if you’re buying a precious gemstone, can give you a certificate from a reputable laboratory.

Who is the Author, Kim Rix | Gemstone Detective | Buying Gemstones in...

Who is the Author – Part 3

The Worldwide book offers the widest, most general appeal, to anyone interested in buying a real gemstone – it looks set to be very popular.  What led to the creation of this book, what sort of topics does it cover and who do you hope will read it?

After I had written the first few books, it became apparent that there was a market for a more general book on buying and caring for gemstones.  It’s great for people who want to know more, but haven’t booked a holiday yet, or who want to buy a gemstone in their home country.  I’ve taken out the country-specific detail, which has enabled me to add a few new topics.

I think the most helpful knowledge I share will be about choosing a diamond engagement ring.  It was my husband’s idea to include an easy-to-follow guide to buying a diamond after confessing that he wished he’d known more about it when he chose our engagement ring 12 years ago.  It’s written to help those who find themselves in a similar position – not knowing anything about diamonds but wanting to put a carat or two on their loved one’s finger.  I talk about the 4Cs in relation to diamonds, the different ring styles and gemstone cuts, and I share some tips on making your holiday proposal one to remember!

There’s a handful of other new topics in the book, but I don’t want to spoil all the surprises!

Who is the Author |

Who is the Author – Part 3

What are your top tips for anyone who wants to buy a real gemstone, such as a diamond, in the UK?

It doesn’t matter where in the world you are buying a diamond from, the exact same rules apply – make sure you buy from a reputable jeweller, and make sure it comes with a certificate – preferably a GIA lab report.

My other suggestion is to buy only what you can afford.  Don’t listen to all the hype about how many months salary you should spend on a diamond – that was a line made up by a well-known diamond company to boost sales in the 1930s!  Buy something that your loved one will enjoy wearing and that will suit the lifestyle you live.

Kim Rix GG GIA

Gemstone Detective

Be sure | Be smart | Buy with confidence

Who is author Kim Rix – part 2


I hope you enjoyed reading Who is the Author – Part 1. In this post, you will discover more about the book series.

How would you describe the Gemstone Detective series to anyone who has never heard of it before?

It’s a simple travel guide to buying gemstones abroad.  It’s a bit like a Lonely Planet or Rough Guide – but it’s just about holiday experiences with gemstones & jewellery.

Most of the books are country specific. The books are for tourists and travellers, whether they are gem collectors, jewellery lovers, jewellery designers, hobbyists, or just holiday makers who want to take home a special souvenir.

Because I’ve been out there to research the gem trade in each of the countries featured, the information is real, up to date and you can trust it.

Who is the Author – Part 2

Your first book, Buying Gemstones and Jewellery in Sri Lanka, first launched in October. Tell us about how that went and what sort of feedback you’ve had on the first book?

The launch was very successful and those who were there have told me they had a great time.  I certainly did – the food was great, and both conversation and bubbly were flowing!

We’ve had some excellent feedback from readers of the book.  We’re racking up more 4 and 5 star reviews from readers on Netgalley, and there is a growing number of equally glowing 4 and 5 star reviews on Amazon – 15 and counting…

It’s been great to see that several people have read the first book and then pre-ordered the rest of the series.  It never even crossed my mind when I began this project that people would want to collect every book!

You’re launching three books in one night tonight – quite an impressive feat!  Why is it important for you to offer such a wide range of books within the series?

Well, when someone refers to a ‘series’ I think there’s an expectation that it’s going to be more than a few books… Of course, I want my books to help as many people as possible.  Offering such a wide range reflects how many options we now have as tourists to travel and explore.  

How long does it take you to write each book? What is the process in terms of choosing a destination?

Each book is a combination of 2-3 research trips, which adds up to about 4-6 weeks research in that country.  I’ve often been to a country a couple of times even before I go back for these research trips. My most recent trip was to India, and that book is now with the printers, ready to hit the shelves in May.

It’s easy to choose countries for the series because I know exactly which tourist destinations have a well-established gem trade.  Not all gemstone-producing countries are suitable, so I won’t be writing a book for Cambodia, Afghanistan or Madagascar just yet – the gem trade is too young and underdeveloped.

Who is the Author – Part 2

Where are you travelling to this year?

I’m heading off to USA next week for a 6-week trip, and I’ll be returning to the USA in May for a further two weeks.

I’m not quite sure how the rest of the year looks yet because I want to fit in a trip to Mogok to finish researching the Myanmar book, and then there’s the possibility of combining a trip to several countries in Africa – South Africa, Namibia, Tanzania and Zanzibar.

When will the next books be released?

India will be published on 14 May 2019, and USA will be published in September 2019. I’m not yet sure about Myanmar but hopefully it will be sometime this year – if I can squeeze in that second trip to Mogok.  It’s going to be a very busy year!

I hope you will join me again for Who is the Author – Part 3

Kim Rix GG GIA

Gemstone Detective

Be sure | Be smart | Buy with confidence

Who is author Kim Rix – part 1


Who is the Author? Over the next few weeks I will tell you a bit about myself and why I am writing the Gemstone Detective series.

Who is Kim Rix?  Why are you the right person to write this book?

I’m a wife, daughter, aunty, cat-lover, gin-drinking, sun-worshipping, 4 ft 11 Ninja!  I’m also a professional photographer, a gemmologist and I love to travel.

Who is the Author, Kim Rix | Gemstone Detective | Buying Gemstones in...

I have a very well-travelled family, who now live all over the world.  Over the years I have listened to their stories, admired their photos and wished my lottery numbers would come up so that I too could pack my suitcase.  As time went on, I found it harder and harder to ignore my wanderlust and realised that I couldn’t just wait for that lucky ticket – I had to get out there and do it for myself.

Something else that had been brewing up inside me for a while was the urge to learn everything I could about gemstones. I had fallen in love with gemstones as a young girl.  At that tender age, all I knew was that my birthstone was amethyst, and that diamonds were a girl’s best friend.  From then on, I grabbed every available opportunity to look at gemstones.  It became a bit of an expensive hobby and maybe even a bit of an addiction!  One day, I decided that I should turn my hobby into something more serious – so I signed up for a course at the GIA.

Then there’s my photography. I’ve had a passion for photography since my twenties. I love capturing the beauty of life in all its guises.  On holiday that usually means wildlife, people, street photography and occasionally landscape photography.  Something that not everyone knows is that 99% of the photography in each book was taken by me on my research trips.

When I had the idea to write this series, it just felt perfect.  I knew the books could help people like the young me – people who loved gemstones but didn’t know much about them. It’s not just my expertise in gemmology that makes me the right person to write these books – I’ve had the bad experiences, myself.  Several years ago, I got caught out in Egypt.  I thought I was buying a real ruby at a bargain price, when in fact it was just a cheap synthetic, made in a lab. If I knew back then what I know now, that wouldn’t have happened!  I don’t want other people to make that same mistake…

You’ve combined three passions into a career – that’s really inspirational!  How did you do it?

It’s easy. Once I came up with the idea, I made a commitment to myself to do it.  About 4 years ago, I was diagnosed with heart disease.  I made a few lifestyle adjustments and I’m fine now, but it was a pretty scary realisation. It really brought home to me how precious life is.  I was determined to get this series underway quickly, because you never know what tomorrow will bring. I believe you have to grab life with both hands and make the most of it while you can.  I’m cramming each day with the things I love!  I’m a self-taught photographer, I’ve always loved things that are shiny and sparkly, and I love travelling and exploring the world.   Writing books which help people avoid buying a fake gemstone lets me do all these things.  Now I life my life with passion, purpose and I’m getting an enormous amount of pleasure doing it!

What do you love most about photography, gemstones/jewellery and travelling?

What do I love most about it all? It’s hard to put in to words – I just love the freedom. I meet so many interesting people. I get to look at lots of lovely shiny things. And I’m seeing the world.

Who is the Author – part 2, will follow in a few days.

Kim Rix

Gemstone Detective

Be sure | Be smart | Buy with confidence