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GUIDE TO BUYING DIAMOND TESTERS

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For instruction manuals, troubleshooting and advanced tips, click here

 

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 (labeled 'paste') was not diamond, the second (labeled 'diamond') was not diamond, the third (labeled 'diamond') was diamond, the fourth (labeled 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 cost over £200.00.

 

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 our best quality diamond tester costs just £75.00.

 

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 in this article I shall answer both questions.

 

HOW 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).

 

HOW 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.

 

ARE 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 model has 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.  If you're not sure which type you prefer, click here to read the instruction manuals.

 

HOW RELIABLE ARE DIAMOND TESTERS? - WHAT ABOUT CUBIC ZIRCONIA AND MOISSANITE?

 

Of the two most common diamond simulates, 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 Moissonite 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 (or combined tester) later. Do you really need a Moissanite tester?  Here are two fascinating facts that might help you make your decision:

 

FACT 1.  Moissanite first grown ('invented') by man about ten years ago, so if you are quite certain that you are testing an antique ring (or anything more than five years old) then the stones  won't have Moissanite.

 

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 Moissantie 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.

ARE DIAMOND TESTERS FOOLPROOF - THE TALE OF A MAN WHO WAS FOOLED

Nothing is foolproof! Supposing, for instance, you bend the test-tip, fill the tester up with coffee, use a flat battery...

I recommend the type with the row of lights that show how fast the machine is reacting, rather than two pre-set lights that tell you YES or NO. 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 South Africa to buy 'bargain' 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.

There are precautions you must take if you are spending large amounts of money and know nothing about diamonds.

Most importantly, 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. Well, perhaps if you go, in person, to the mines in the most war-torn parts of the world, traveling for days through barren land, braving road blocks and gunmen...

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 South 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. It is also possible, with any machine made by man, that the machine develops a fault - so use those four 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're become agitated it might be because the stone is rapidly reaching room temperature and is about to register NOT DIAMOND on your tester.

All of this advice refersto the type of diamond tester (the type we recommend) that has a row of lights. The type with two lights to indicaate YES or NO when buying diamonds is not suitable for buying rough (uncut)stones and will be fooled most of the time.

Also, these precautions do not apply in everyday dealing where the amounts of money involved are relatively small, there is no need to become paranoid!