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Gem Alert – Never A Dull Moment

Recently, an eternity ring was sent into our lab. The jeweller who sent it asked that we verify the ring’s five blue stones.

One way to identify natural sapphires is the intersecting needles. Under magnification, we could see that these beautiful stones showed just such needles – just what you’d expect from a Sri Lankan or Burmese natural sapphire.

But when we looked a little closer, the truth was revealed.

A more thorough inspection included immersing the stones in methylene iodide. The refractive index (RI) of methylene iodide (1.741) is very close to that of sapphires (1.76-1.77). The result is that the stone seems to disappear in the liquid, leaving only internal characteristics visible – inclusions or growth features, for instance.

What we found was astonishing. These stones were actually garnet-topped composite stones. In the photograph below, you can see that the top is red, while the bottom is blue. This colour difference would never have been visible without immersion.

Rutile needles can also be present in garnets as well as sapphires, so it’s no surprise that these stones could be passed off as sapphires.

It’s in cases like these that thorough knowledge of both the stones and the cons – not to mention many years of experience – come into play. Well done to the jeweller who sent this ring in to be checked!

Gemstone cons get more sophisticated all the time. It’s important to make sure that the stones you sell are the genuine article. Your reputation as a jeweller depends on it! To guarantee the authenticity of your gemstones, contact The Gem Lab for certification on 021 761 1746, or email me on

This is a picture of the eternity ring that was sent into our lab. The jeweller who sent it asked that we verify the ring’s five blue stones. Under magnification, we could see that these beautiful stones showed rutile needles – just what you’d expect from a Sri Lankan or Burmese natural sapphire.
These stones were actually garnet-topped composite stones. In the photograph, you can see that the top is red, while the bottom is blue. This colour difference would never have been visible without immersion.
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Fracture Filling versus Iridescence

Have you ever seen a stone with tiny (or perhaps not so tiny) fractures? Chances are, you have. Most people have at least one fractured stone in their collection – often without even knowing it. Fractures can mar a gem stone’s natural beauty. To improve the gem’s appearance – and value – these fractures are often filled.

It’s a common practice, and one that people find hard to spot. Many gem stores and jewellers have a policy of never selling these stones. But it can damage a store’s integrity when they accidentally sell a fracture filled stone without realising it.

Some fracture filled stones sometimes look similar to flawless or lightly included stones. This makes it easy to mistake one for the other.

And in fact, some gemstones have been identified as having been fracture filled, when they haven’t been.

A basic rule to remember is that fracture filled stones display a blue (or, in the older treatments, red) ‘flash’.

That means that as you examine the stone and rock it from side to side, the ‘flash’ effect will ‘switch’ on and off.

Iridescence is like oil on water. As you move the stone from side to side the colour will change, too. But in this case, the colours seem to shift along the fracture through the colour spectrum like a rainbow.

A little bit of training can go a long way to ensuring your team doesn’t make a mistake. To learn more about correctly identifying gemstones and their treatments, join our one day Basic Gem Identification course. 

‘Flashing’ blue colour will ‘switch’ on and off as you rock the stone from side to side Iridescence will move through the rainbow colours as you rock the stone from side to side.
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All that glitters is not gold

We’ve all heard the saying before, and it’s as true for gem stones as it is for precious metal.

The end of the year brings its share of festivities as folk start planning their year-end gifts and celebrations. It’s a good time to consider how to invest our hard-earned cash (and gems and jewellery can be a good vehicle for investment!). It’s a time of reflection and recognition – a time we should all enjoy.

Unfortunately, it’s also a time when the less-than-ethical few grab the opportunity to make a little holiday cash, too. Well, a lot of holiday cash, if they can.

And gemstones are a wonderful way to deceive people.

You may have seen the old con on Carte Blanche recently []. Clever con-artists have managed to reel unsuspecting businessmen into the thick of a clever gemstone sale. The attraction? Quick and substantial profits. But once victims pay over hundreds of thousands to the syndicate, all they are left with is a handful of worthless stones.

That strategy has been around for some 15 years, if not more.

On the program they illustrated using a Polariscope to separate the fake from the tanzanite. But these tricksters don’t only use glass. Nowadays, they also use clear quartz crystal, dyed to fool the unsuspecting buyer. If you examine it through a loupe, you will see the natural inclusions of the quartz. The polariscope will give you the same result for tanzanite and quartz, as they are both doubly refractive.

Below you will see a better way to distinguish between tanzanite and either clear quartz or glass imitating tanzanite. Here we’re using a pair of sunglasses. You only need one polaroid. The picture on the left is of a tanzanite showing a violet red colour. When the sunglasses are rotated, it has a more bluish colour. This effect is caused by certain optical properties of tanzanite. Because glass and clear quartz don’t share these qualities, they don’t have the same effect.

In our trade, it’s easy to believe a gem trader would track us down to invest in high value stones. After all, it’s what we do. But that means we need to be even more careful not to get caught in a confidence scam. The effect can cost us and our clients money – not to mention the damage it does to our reputation!

Before you invest money in beautiful gems from someone you’ve never bought from before, give me a call. Certification is quick and inexpensive – and it can save you thousands!

Tanzanite1 Tanzanite2
Tanzanite viewed through polaroid sunglasses. You can see the violet red colour By rotating the polaroid sunglass 90 degrees you can see an obvious change in colour.
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Convincing Tanzanite Imitation

Tanzanite is a beautiful gemstone. And it’s becoming more and more popular … so much so, it has become one of the best selling coloured stones on the market today. Sadly, this means that we are seeing an increase in both imitations and coated tanzanites. As the imitations become more sophisticated, more and more of them are passing through the trade undetected.

Some of our clients have lost a lot of money.

That’s why it’s so important to stay ahead of these developments – and why I am emailing you again so soon, to let you know what is going on.

In my last blog, I made you aware of the rough tanzanite imitations doing the rounds. We also looked at how to distinguish between uncut clear quartz, glass, and tanzanite.

As I mentioned in that email, I am seeing a fair amount of faceted glass coming through, being passed off as tanzanite. Glass makes a wonderful imitation. As you can see from the pictures below, under tungsten light the glass takes on a violet colour. And under daylight (or equivalent), the glass takes on a more violet blue colour – very much like tanzanite does.

The refractive index of this glass is around 1.70 – which also overlaps with tanzanite (RI: 1.69 – 1.70). The difference is that glass is singly refractive. It will only give one reading – no matter what direction you take the RI.

Tanzanite will give two.  ALWAYS make sure you get two readings! Also take an RI reading from different facets around the stone – even from the pavilion if you only get a single reading, to be absolutely sure. You won’t get two readings from tanzanite if taken in the direction of the optic axis.

Some of you use a tanzanite filter to separate tanzanite from the imitations. But the latest tanzanite imitations I’ve seen, made from glass, also show red through the tanzanite filter. One can no longer distinguish between glass and tanzanite just by using the tanzanite filter.

If you’re not sure, or you’d like assistance, please give me a call or send me a message. I’d love to help.

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Too good to be true? Probably…

As the year rushes to a shopping-frenzied close we just had to bring you this quick warning about the latest gem stone fraud doing the rounds.

In recent weeks we’ve seen an increase in con artist activity. These fraudsters are trying every trick in the book to sell synthetics, imitations and treated gems as natural stones – without disclosing the true nature of the stones.

There has also been an increase in black moissanite being sold as black diamond; glass being sold as tanzanite; coated tanzanite; and fracture-filled rubies and sapphires passed off as authentic.

Our goal at the Gem Lab is to keep you and your customers safe from fraud this festive season … and all year round, too! We are fully equipped to certify and authenticate the colour of black diamonds and identify all gemstones.

As mentioned in our previous email we are NOT closing over the Christmas period so that we can be of service to you.

Call me on 021 761 1746, 082 653 4567 or email and make sure your gems are what they seem.