Moissanite, its composition and manufacture (how synthetic Moissanite is synthesised).
How to tell diamond from Moissanite: diamond testers, Moissanite testers and multi testers.




Moissanite tester
Diamond testers


Moissanite testers
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Moissanite is a manmade stone that looks like diamond. Its significance is that it tests as 'diamond' on diamond testers. Therefore, if you have a standard diamond tester, you will also need a Moissanite tester (though it's far simpler to get a 'Multi' tester that tests for both). The method is: test the stone on a diamond tester, if it reads diamond, it is either diamond or Moissanite - you won't know which. Then test the stone on a Moissanite tester to see if it is Moissanite. If it registers diamond on a diamond tester and not Moissanite on a Moissanite tester - then it's diamond.

Of course, it's far easier to get one machine that tests both, a Multi-tester.

There is a general article about testing diamonds.
Or if you want to know about how the testers work, this is included in our troubleshooting guide
Or read on if you want to know about Moissanite.



Moissanite is a manmade stone (it doesn't exist in nature in a form that can be cut into gemstones*). It was 'invented' in the 1990s, its only significance is that it 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. Moissanite is not a 'type' of diamond, it is another stone altogether.

* It's found either as tiny black crystals of Silicon Carbide (which can be synthesised to form the abrasive 'Carborundum') or as tiny platelets. You can see pictures of Moissanite crystals here, but they are green, less than 1mm in size and cannot be cut into gemstones. Part of the publicity about Moissanite is true: that the French chemist Henri Moissan (hence "Moissanite") discovered the mineral in a meteorite crater in Arizona in 1893. But the gemstone stems from a 1998 patent for "translucent silicon carbide of a single polytype that are grown in a furnace sublimation system" - i.e. they are grown in a furnace in a laboratory.



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 atomic structure (it does not contain nitrogen, it does contain boron) and this makes the diamond electrically conductive, i.e. it will register 'Moissanite' on a diamond tester.

Unless you are a diamond dealer handling diamonds every day, 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 discover that their diamond registers 'Moissanite' on a Moissanite tester.

Incidentally, TYPE II diamonds are 'rare' by an accident of nature, due to their atomic structure, they are not 'rare' in the sense of being more valuable than 'ordinary' diamonds, they are exactly the same. In fact, logic dictates that it would be more difficult to sell a diamond that registers 'Moissanite' on a tester!

* The current travels all the way from your hand, through the metal plates on the tester, through the stone, through the setting of the jewellery, to your other hand, all the way round your body, back to your first hand, and back into the tester - so it is essential to hold the tester with your finger on the metal plate of the tester.



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 type of UV light was required. To his amazement he found that any UV light worked. 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 Experior) tester, there is a UV light built in to the tester, and ours 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).


Moissanite tester

Moissanite registers as 'diamond' on diamond testers. That is why you need an additional tester (a Moissanite tester) to detect Moissanite.

Moissanite is electrically conductive (very couldn't measure it on an ordinary electric meter) - and this is what a Moissanite tester detects.

Many other objects are electrically conductive; many other gemstones are electrically conductive. However, diamond (with one very rare exception) is not electrically conductive.


- test the stone on a diamond tester
- if the tester reads 'diamond', it is either diamond or Moissanite.
- then
test the stone on a Moissanite tester, if the tester reads 'Moissanite' then the stone is not diamond (though there is one very rare exception).

If you already have a diamond tester, buy a Moissanite tester.

If you don't have a diamond tester, your best-buy would be a multi-tester which is a combined diamond tester / Moissanite tester.

If you don't feel you can justify spending money on a mult tester, choose a diamond tester plus a Moissanite tester, you can (if you wish) opt for for cheap models and save money.

If you really wanted to save money, you could buy the very cheapest diamond tester and a Moissanite tester...though, personally, I wouldn't go for 'the cheapest' - they are never as reliable as the better models.


The complete guide to testing diamonds



Diamond tester trouble shooting

A lot about electronic gem testers

A little about optical gem testers


See also: all articles on this website or latest articles on this website




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