TO BUYING DIAMOND TESTERS
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here for an overview of diamond testing
What about Moissanite? - using testers to tell diamond from Moissanite
you intend going to Africa to buy 'cheap' diamonds, scroll down or click
All information articles (including Qucktest product reviews)
The following story is a warning to anyone who thinks that having a machine (any machine) is guaranteed to get them a bargain.
We sold a diamond tester to a man who went out to Africa to buy 'bargain' diamonds (uncut 'rough' diamonds) from a 'contact'. After a very long time haggling they agreed a price (I think it was $50,000.00), he tested the stones, they registered DIAMOND on the tester, they were sealed in a container and the he signed across the seals. The money was transferred into the seller's bank account and the following day the buyer collected the stones. The seals on the container were still intact. And guess what? When he got them back to England he found they weren't diamonds at all. The customer rushed the diamonds over to us, we tested them on five different diamond testers - they were not diamonds.
This, in a way, was a clever 'con' - because the average jeweller will know what a cut diamond looks like, and if presented with huge stones that look 'too watery' or 'too sparkly' he will be suspicious, even before turning on the diamond tester. But very few people know what diamond crystals look like. If you are planning on parting with thousands of pounds, do some research and find out!
There are other precautions you can take if you are spending large amounts of money and know nothing about diamonds.
Firstly, if the deal seems too good to be true, it's because it is too good to be true, "Cheap Diamonds" are like "cheap gold" or "cheap cash" - they simply don't exist...unless you become involved with criminal gangs. These gangs (according to the many press reports) also smuggle real diamonds, drugs and people, and you really do not want to find yourself in a remote part of the world, taken by gunmen to remote mines, then pressurised into parting with money.
Do not let that diamond tester out of your sight, even for a minute. They can be tampered with (by re-soldering wires inside) so that everything reads DIAMOND. Our man in Africa managed to return to England without the diamond tester, it had been "mislaid in the confusion" - what a surprise!
Keep on your person a genuine diamond (it need not be large) and a paste (glass) and a sapphire (a small synthetic sapphire will do) and test each of them before testing your purchases. You will then know if the diamond tester has been tampered with. If you want to be quite certain, buy a set of test-stones (seven stones used to imitate diamond, all 'brilliant cut', just like diamond).
It is also possible, with any machine made by man, that the machine develops a fault - so use those three stones to check the machine.
Tricksters have been know to store stones in ice to cool them so that the diamond tester falsely reads DIAMOND. Try touching the stone gently against your upper lip to see if it feels icy cold, try clasping it in your warm hand and chatting to the sellers for five minutes. If they become agitated it might be because the stone is rapidly reaching room temperature and is about to register NOT DIAMOND on your tester.
These precautions do not apply to everyday dealing where the amounts of money involved are relatively small, there is no need to become paranoid. And I did sell a diamond tester to someone who was going to Africa, but who had recommendations from friends who lived there, and he was happy about who he was dealing with and, as far as I know, the transaction was successful. Whether he made a profit I have no idea!
BEWARE OF UNUSUAL STONES...AND ALWAYS BE AWARE OF THE OBVIOUS
One stone that caused prolonged correspondence on an internet forum for gemmologists, was an unknown stone bought as 'black diamond'. It was opaque, so the usual examination of inclusions, under a microscope, was not possible; the surface was 'pitted' like granite; the SG (specific gravity) wasn't quite right; and although it certainly registered 'diamond' on a diamond tester, the results on a Moissanite tester were inconclusive, it depended on where, on the stone, the probe was placed.
Even without a gemmolgist spending a few hours examining and testing the stone, there were two causes for alarm. Firstly, it was bought by a serviceman in Afghanistan, and most stones sold to servicemen in this area are not genuine. Secondly, 'proof' that it was natural black diamond came in the form of a lab report (certificate) from New Delhi, from "an ISO 9001:2008 Company comprising GIA alumni." A certificate is worthless unless you can check that the company (and the certificate) is genuine - and even then, you need the skill to match the stone with the certificate.
Gemmologist's conclusion: it was not diamond, it was Moissanite.
My conclusion: electronic
testers are not suitable for detecting black stones.
Some models of diamond tester have a built-in UV light, and this has led to the quite logical assumption that UV light can be used for testing diamonds. This is not true. There is absolutely no way you can distinguish diamond from non-diamond using UV light. The only useful thing to know is that diamonds fluoresce (glow) randomly. So if you have a cluster ring or a diamond brooch and all the stones react in exactly the same way (whether they fluoresce or not) - they are probably not diamond; if some fluoresce and some don't...then they might be diamond...but they might not.
UV light does, however, has some use for gemmologist because it can give an indication of probability when comparing natural diamonds with synthetic diamonds (see 'Explanation' at the bottom of this section). For examining 'parcels' of diamonds you will need a UV lamp that provides long-wave (this is the type we sell, this is the type on the diamond tester) AND a short-wave UV light (which we don't sell). View the stones on a black background in a completely dark room (or a special UV viewing cabinet). Natural colourless diamonds (of which about 40% fluoresce) usually fluoresce more under long-wave than under short-wave; some synthetic diamonds have just the reverse reaction, the fluorescence is weak (or nil) under long-wave, and strong (or stronger) under short-wave. If, therefore, you buy loose diamonds it could be worthwhile checking each parcel under UV light to judge the probable mix of 'naturals' and 'synthetics'. But examining a diamond under a UV light will tell you nothing. This information is for the gemmologist or professional diamond dealer, the average jeweller or antiques dealer does not need to know any of this.
UV light can also be useful when grading a diamond for colour, because white diamonds that fluoresce under UV light also fluoresce under UV light present in daylight, and this can make the stone appear a better colour than it really is, so you may wish to downgrade it by one or two colour grades. Again, this information is for the gemmologist or professional diamond dealer, the average jeweller or antiques dealer does not need to know any of this.
EXPLANATION: 'Synthetic' does NOT mean 'imitation' - a synthetic stone is grown in the laboratory to the same recipe found in nature, and the aim of the manufacturer is to make an end-product which is identical to its natural counterpart. Synthetic diamond IS diamond (unlike, for instance, Cubic Zirconia or Moissanite which are not diamond) - and synthetic diamond registers DIAMOND on diamond testers...because it IS diamond.
Moissanite is a manmade stone (it doesn't exist in nature in a form that can be cut into gemstones). It is not common, it was only 'invented' a few years ago, its only significance is that is registers 'diamond' on diamond testers. Moissanite does, to the non-expert, look remarkably like diamond - but it is not diamond it is Moissanite, i.e. Moissanaite is not a 'type' of diamond, it is another stone altogether.
MOISSANITE TESTERS AND TYPE II DIAMONDS
Moissanite testers work by measuring electrical conductivity through the stone. Diamond is not electrically conductive, Moissanite is. However, there is a very rare type of diamond which has an unusual chemical composition (it does not contain nitrogen, it does contains boron) and this makes the diamond electrically conductive, i.e. it will register 'Moissanite' on a diamond tester.
If you are not a diamond dealer handling thousands of diamonds, it's unlikely that you will ever see one of these. But, rare as these diamonds are, they are turning up at gem laboratories, sent in by anxious retailers following complaints by their customers (who have bought an expensive diamond only to find it registers 'Moissanite' on a Moissanite tester!). Testers to distinguish Type II diamonds cost a few thousand pounds.
For the general jewellery or antiques dealer, a Moissanite tester is highly unlikely to test Moissanite as diamond (which would cause the dealer to spend money on a near-worthless stone), but on very rare ocassions it might test a Type II diamond as 'Moissanite'. Testers to distinguish Type II diamonds cost a few thousand pounds.
MOISSANITE TESTERS AND UV (Ultra Violet light)
Unlike diamond testing, UV light does make a difference when testing a Moissanite on a Moissanite or combination (multi) tester.
The discovery was made by a gemmologist who worked out that, according to the laws of quantum physics, UV light should make a difference to electrical conductivity. He then took a deep breath and set about finding out just which exact wavelengths of UV light were required. To his amazement he found that any UV light would work. Moissanite testers that don't work on some 'difficult' Moissanites (rare as they are) work perfectly when the stone is exposed to UV light.
If you are buying a Moissanite tester, buy a UV light too, they really are not expensive (see how UV light works). If you are buying our combination (multi) tester, there is a UV light built in to the tester, and this is the only model that will enable you to shine the UV light on the stone whilst testing (other models give you the choice of testing the stone or using the UV light, but not both at the same time, which isn't really of any use).
DT-4 £75.00 (with UV light)
here or go to our page of testers to buy one (not in our mail order
catalouge). We do sell the 'bargain' diamond testers that
you see everywhere on the internet (we like to be competitive) but please
be aware that these are not the 'best' testers. We usually have a selection
of one-off samples bought from around the world.
RECOMMENDATIONS: MOISSANITE AND MULTI TESTERS
MULTI II £139.00
There's a manmade stone called Moissanite that registers 'diamond' on diamond testers. The 'multi' is not fooled by Moissanite. It will light up "Diamond" or "Moisanite" (or "Other stone" if it is neither, but it does not tell you which other stone). Moissanite is not common; Moissanite is not valuable; Moissanite was only 'created' by man a few years ago and so should not turn up in old jewellery - but you won't know if you have a Moissanite if you have a diamond tester.
MOISSANITE TESTER £45.00
If you already have a diamond tester an are happy with it, then buy a Moissanite tester. If you want the best diamond tester (DT-5) which is adjusted for cold weather / large cold stones and also want to test for Moissanite, then buy the DT-5 plus the Moissanite tester.
To cover all possibilities,
the MULTI II will also distinguish Moissanite, which registers diamond
on diamond testers. It has the same sensitivity as the DT-4 so allow plent
of time for cold stones to warm up to room temperature. Or if you want
the best of all worlds, buy a DT-5 plus a Moissanite tester.
FOOTNOTE - what else is special about the DT-5?
It is based on previous models that we have been selling for many years, but we have 'tweaked' the specification. The main change is that we've made it less sensitive so that it doesn't give a false 'diamond' reading on large rubies and sapphires (and any large cold stone).
Not being able to cope with cold stones seems to be a fault caused by the Chinese / Japanese idea of 'cold'. When they design these testers they simply have no conception of working at an outside market in the winter in temperatures close to zero, and some models (not ours!) tell you not to use them in 'cold' conditions of below 18 degrees centigrade.
We have made other changes too. We have completely re-written the instruction manual so there is no need to battle with a free translation from Cantonese or Japanese. We have re-labelled the controls, the knob is now correctly labelled 'Sensitivity' rather than than the confusing 'Volume'. The new labelling also makes it clearer as to which lights indicate 'diamond'. We have extended the number of segments from 8 to 9. The chart on the back of the tester shows sizes of diamonds as circles actual-size, rather than a grid of figures.
OVERVIEW / GENERAL QUESTIONS ABOUT DIAMOND TESTING
Here is an article, by Raffi at Quicktest, originally published in the Antiques Trader newspaper:
I once walked into a local shop (it sold crafts and coins and the odd antique…and little bit of jewellery) and I said, "Hello Edward" (he didn't like being called "Ed") and I showed him one of our small battery-operated diamond testers.
"Why would I want one of those?" he said, pointing to a handful of stone-set rings in his window.
Upon testing the first four rings this is what he found. The first (labelled 'paste') was not diamond, the second (labelled 'diamond') was not diamond, the third (labelled 'diamond') was diamond, the fourth (labelled paste') was diamond - he bought the diamond tester.
Again and again customers at the fairs say, "If only I'd had one of these last week when I was buying a 'parcel' that contained stone-set jewellery!"
We sell most of our diamond testers by mail and customers don't actually make a special point of writing to say how wonderful it is - but there are very few complaints. In fact, the latest diamond testers are so reliable that virtually all complaints concern dogs ("The diamond tester worked fine until the dog chewed it") or tea ("I don't know WHY it doesn't work any more, do you think it might be because I spilt tea in it?") or the Bermuda Triangle ("I lost it").
Long ago a diamond tester was a big square box of electronics with a probe, you plugged it into the mains, waited two minutes for it to warm up, pressed the probe on the stone, waited for a reaction, and they were expensive.
Today a diamond tester is small (the size of a tube of toothpaste), takes one standard battery, you wait twenty seconds for it to warm up, press the probe against the stone, and get a reading immediately. And they are not expesnive.
Many customers say, "How does it work?" I never answer the question because they don't usually mean "How does it work?" they mean, "How do you work it?. But I shall answer both questions.
DO YOU WORK A DIAMOND TESTER?
Switch on, hold it like a pen, wait for it to warm up (when the READY light shows), press the tip onto the stone, if the row of LED lights light up quickly (and there's a bleeping sound) then you have a diamond, if the lights don't move at all it is not diamond, if the lights move very slightly you probably have a ruby or sapphire (though a diamond tester is not designed as a ruby - sapphire tester). There is also a safety feature that sounds an alarm if you accidentally touch the mount instead of the stone (which avoids false readings).
DOES IT WORK?
Heat. Or, to be more precise, Thermal Conductivity. You may have seen traders 'testing' stones to see if they are paste or 'real' by touching the stone against the lip. They are feeling (not very scientifically) for "coldness." Plastics (and maybe glass) feel warm-to-the-touch, many gemstones (probably) feel cold to the touch, as I say, it's not very scientific. This relative coldness is what the tester is measuring, Thermal Conductivity.
THERE DIFFERENT TYPES OF DIAMOND TESTER?
The most common type of diamond tester works on the principle of Thermal Conductivity. There are two slight variations. The cheaper models have two lights, one for Diamond and one for Not Diamond, the best model has a row of lights. The advantage of the better model (row of lights) is that you can turn the sensitivity down if you are working in the cold (e.g. an early morning market), the cheaper model (two lights) will give false readings if it is cold.
RELIABLE ARE DIAMOND TESTERS? - WHAT ABOUT CUBIC ZIRCONIA AND MOISSANITE?
Of the two most common diamond simulants, Cubic Zirconia (including 'diamond-coated' Cubic Zirconia) presents no problem at all but Moissanite needs a special mention. Moissanite is a purely synthetic stone (ie it is grown in laboratories by man, it does not exist in nature) and it registers as diamond on diamond testers. This is an unfortunate fact of physics, that Moissanite has the same thermal properties as diamond. So how do you tell Moissanite from diamond? There is another electronic tester, it looks (and operates) just like a diamond tester though it works on an entirely different principle. Or there is a combined electronic tester for diamond and Moissanite.
Do you need a diamond tester and a Moissanite tester? Most people buy only the diamond tester; most people buy the diamond tester "just to start with" and some buy the Moissanite tester. Do you really need a Moissanite tester? Here are two fascinating facts that might help you make your decision:
FACT 1. Moissanite was first commercially grown ('invented') by man in 1995, so if you are quite certain that you are testing an antique ring (that hasn't been tampered with) then the stones won't be Moissanite. The origin, as a mineral (Silicon Carbide) found in meteorites, dates back to 1893 but cannot be used as gemstones, quite contrary to the publicity that implies that this is a rare as-good-as-diamond gemstone tha comes from outer space. Not true.
FACT 2. Moissanite hasn't quite taken off in the way that Cubic Zirconia did, probably because the smallest Moissanite costs several pounds whereas Cubic Zirconia costs a few pennies, so Moissanite isn't that common. However, it's main purpose (it seems to me) is to fool antiques dealers, usually with a story about the item of jewellery having been in the family for many years.
So if you are trawling the fairs and boot sales and are happy that the items you see are genuinely old, you will probably be OK with just a diamond tester, but if you set up shop and advertiser that you buy jewellery you will attract the fraudsters, so make sure you have a Moissanite tester too.
Finally, there are testers that will test both diamond and Moissanite (i.e. one tester to test both). The advantage is that you only need one machine instead of two, and also it costs slightly less to buy the combined tester rather than two separate testers. The disadvantage is that you do have to follow the instructions precisely (unlike diamond-only testers which are very simple to operate).
Whichever you choose, you will need good eyesight (good enough to see the tip of the tester and the very centre of the stone) and a steady hand. I have watched many people who have neither of these attributes and will never, ever, be able to use a tester, at best they 'sometimes' get it to work.
QUICKTEST, Watford, WD18 8PH, Tel. 01923 220206, email info(at)quicktest.co.uk