Gemstones: how hard is hard and does it matter anyway?

Posted By: PSJ Yeovil, 6th January 2016 Tags: Gemstones , Diamonds

I was very excited when a customer recently brought in a ring that she said was set with a "synthetic diamond". Being aware that some very impressive synthetic diamonds are now being manufactured, I was quick to examine it in detail with a lens.

One look with my jewellers lens (loupe) immediately told me it was not a diamond but one of the excellent diamond simulants such as synthetic cubic zirconia (CZ) or moissonite (it proved to be the former). How was this so simple?..... the answer lies in the unique hardness of diamond  sharp to a degree unachievable with any other gemstone; they are also permanent and indestructible in normal wear.

Now the terms synthetic and simulant are frequently confused. A true synthetic diamond is chemically and physically identical in every respect to its natural counterpart, but it is man-made using highly demanding techniques developed quite recently. A cut and polished synthetic to all intents and purposes will look exactly like a natural diamond. 


In contrast however, many simulants have long been used to imitate diamond in jewellery. For example, you may find white quartz, white sapphire, white topaz or even glass(paste) set to imitate diamond in Victorian or earlier jewellery. They were quite commonly used as inexpensive diamond substitutes and although modern synthetic CZ and moissanite are far more convincing, none of these has the wearing qualities or appearance of diamond.

Other common synthetics include emerald (since the early 1960s) and ruby and sapphire from the late 19th century. In all of these, the basic appearance and hardness are exactly the same as the natural gem, but their different origin is clear under a loupe!

So in what other ways are the hardness of your gems important? Be aware for example, that diamond(10)* is 4 times harder than sapphire(9)*, which is 2 times harder than topaz(8)*, so the answer partly depends on where and how you want to wear your favourites. 

rubbed peridot

You may find  the allure of Tanzanite irresistible because of its tantalising rich purple hue; but a few words of caution-- its low hardness(6.5)* can make tanzanite unsuitable to be worn every day as a ring.  As a pendant, your beautiful  tanzanite can be truly long-lasting but set in a ring, tiny chips and scratches can quickly turn that vibrant gem into a rather dull stone (Compare the worn Peridot above).

If you have worn or rubbed gems in your older ring or bracelet, bring it to us at PSJ: we might be able to repolish them to look just like new again!

*Moh's scale of hardness

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