Distinguishing diamond from synthetic Moissanite

See all diamond and moissanite testers.

Every tester has its limitations, no matter what the make or model. This article is about testing for Moissanite. For a advice on diamond testers see our guide to buying diamond testers; for a guide to testing gemstones see our guide to buying electronic gem testers. You might also be interested in testing synthetic diamonds.

CONTENTS

MOISSANITE
MOISSANITE TESTERS, QUICK GUIDE
MOISSANITE TESTERS, DETAIL
MOISSANITE TESTERS AND TYPE II DIAMONDS
MOISSANITE TESTERS AND UV (Ultra Violet light)

MOISSANITE

Summary

Moissanite is a manmade stone (it doesn't exist in nature in a form that is used in jewellery). It was 'invented' in the 1990s, its only significance is that it registers 'diamond' on the cheaper (thermal conductivity) diamond testers. Moissanite does, to the non-expert, look remarkably like diamond - but it is not, it is  it is another stone altogether, it is silicon carbide (the same silicon carbide that is marketed as the abrasive carborundum)*. 

* But carborundum crystals are very small and very black, not suitable for jewellery. 

Detail

Part of the publicity about Moissanite is true: that the French chemist Henri Moissan (hence "Moissanite") first discovered the mineral (crystals) in a meteorite crater in Arizona in 1893. They (natural Moissanite crystals) have since been found in Israel. None are suitable for cutting into gemstones.

Natural Moissanite crystals are:  

• small, mostly 1 or 2mm, found as 'platelets (and they are extremely rare)
• slightly larger, 3 or 4mm crystals (even rarer).
• mostly dark green to light blue in colour
• usually damaged and/or embedded in volcanic rock.

We don't know these have ever been found as 'gem quality' and colourless, suitable for cutting into gemstones; it is safe to assume that natural Moissanites do not exist as gemstones. 

As a gemstone Moissanite stems from a 1998 patent for "translucent silicon carbide of a single polytype that are grown in a furnace sublimation system" - i.e. it is manufactured in a furnace in a laboratory. That is why it's called synthetic Moissanite. And, as synthetic Moissanite, they can be made large, colourless, and almost free of inclusions.

MOISSANITE TESTERS, QUICK GUIDE

Moissanite is a manmade (synthetic) stone that looks like diamond. It is not diamond. It Its significance is that it tests as diamond on the cheapest (£22.50 to £82.50) diamond testers (technology: thermal conductivity).

The better testers (£199.50 to £359.00) use two testing methods in just 2 or 3 seconds (technology: thermal conductivity as above PLUS electrical conductivity) - our most popular model is the Multi-exp) which tests for diamond and Moissanite (and rubies and sapphires). It is the second test (electrical conductivity) that is specifically for Moissanite. That is to say, it detects most Moissanite. Some Moissanite will test as 'diamond'.  

If you already have a thermal conductivity tester you can buy the electrical conductivity type (for Moissanite) on its own, £79.00. But ONLY if you already have a thermal conductivity tester, it won't work on its own.  

The best testers (technology: ultra violet absorption) £995.00 or £1149.00 reliably distinguish Moissanite from diamond (though please note, there is no tester in existence that is "100% accurate"). 

The reason for telling you about the technology is because each type has its limitations. See our comparison chart listing every diamond tester and gem tester, along with the advantages and limitations of each technology. This will help you choose a tester. But this article is only about Moissanite  

MOISSANITE TESTERS, DETAIL

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

However, there are two problems:

1) in the last couple of years the manufacturers have found a way to make Moissanites that are have such low electrical conductivity that they can read 'diamond' on most Moissanite testers. So how do you know? Simple answer: our latest Moissanite testers are super-sensitive and do work on most Moissanites, but if you buy a cheap Moissanite tester (which we no longer sell) or if you have an old model, it will not be at all accurate.  

2) making Moissanite testers super-sensitive has the disadvantage that some synthetic diamonds (not to be confused with non-diamonds!) read 'Moissanite'.

Please be aware that it is not only Moissanite that is electrically conductive. Many other objects are too, including your fingers and your fridge (and some other gemstones). Therefore, only use a Moissanite tester on items you known might be diamond (i.e. not your finger or your fridge) and which you have tested on a standard (thermal conductivity) diamond tester. 

If you already have a diamond tester, and you really want to keep the price as low as possible, buy a Moissanite tester.

If you don't have a diamond tester, we recommend the multi-tester which is a combined diamond tester / Moissanite tester that also tests for ruby/sapphire. The best (and by far the most accurate ) testers are the Arete and Ari.

MOISSANITE TESTERS AND TYPE II DIAMONDS

Moissanite testers work by measuring electrical conductivity through the stone*. Most diamond is not electrically conductive, most Moissanite is. However, 2% of  natural diamonds ('Type II') have an unusual atomic structure (they contain boron instead of the nitrogen) and this makes the diamond electrically conductive, i.e. they will register 'Moissanite' on a diamond 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. In fact, logic dictates that it would be more difficult to sell a diamond that registers 'Moissanite' on a tester!

* The electrical resistance is measured all the way from from the stone, through the metal plates on the tester to your hand, then all the way round your body, back to your hand, and back into the tester - so it is essential to hold the tester with your finger on the metal plate of the tester. 

MOISSANITE TESTERS AND UV (Ultra Violet light)

Unlike diamond testing, UV light does make a difference when testing a Moissanite on a Moissanite tester (or multi tester). It makes the stones more electrically conductive. This is important because now that manufacturers are  making Moissanite with very very low electrical conductivity, the UV light built into the testers aren't always good enough. We recommend the UV1-1-3W.