Is That a Real Diamond? Discussing Simulants & Synthetics

The hardest naturally occurring mineral on Earth, diamonds have been coveted by humans for thousands of years. Their hardness makes them durable stones that can easily withstand daily wear (hardness is different to toughness and diamonds can be broken, contrary to popular belief), and the way they deal with light means they sparkle beautifully. Man has cut and polished rough diamond crystals into many beautiful shapes over the years, and diamond remains the most sought after gemstone in jewellery today.

Only about 20% of diamonds mined have a clarity rating considered good enough for jewellery, and of those, high clarity stones are even rarer, since all diamonds have inclusions to one degree or another. These make diamonds, especially large ones, very expensive stones indeed. This expense, coupled with the ethical concerns over the mining of diamonds, have given rise to a number of simulants, synthetics and treatments. Below we discuss these in more detail.

High quality diamond ring
Unrivalled beauty: a VVS clarity, G-H colour, diamond cluster ring.


Diamond Simulants

Some diamond simulants are natural – stones that, like a diamond, have come from the Earth. While a natural simulant may look similar to a diamond to an untrained eye, it does not have the same optical, chemical & physical properties as a diamond. Examples of natural diamond simulants include white sapphire, topaz and zircon.

Other diamond simulants are synthetic – stones that have been made by man in a laboratory. The most commonly seen of these is cubic zirconia, not to be confused with zircon above. Other synthetic diamond simulants include synthetic moissanite, synthetic sapphire, synthetic spinel and of course, good old-fashioned glass.

cubiz zirconia vs diamond
A marquise cut cubic zirconia ring.

Synthetic Diamonds

Synthetic diamonds are different to diamond simulants. A synthetic diamond shares the same optical, chemical and physical properties as a diamond mined from the earth, but unlike natural diamonds which are aged between 1-3.5 billion years old, synthetic diamonds have been grown by man in a laboratory over a period of weeks. Synthetics account for 99% of industrial use diamonds, and only a very small 1-2% of the gemstone market. Like natural diamonds, synthetic diamonds may be colourless or they may be fancy coloured: yellow, pink, brown, blue etc depending on the amount of nitrogen, hydrogen or boron present, or the affects of irradiation. Synthetic diamond production for the jewellery market has grown significantly over the last 5 years, and output continues to develop and increase.

Diamond Treatments

Just because you’ve found that perfect diamond, doesn’t mean all is well just yet. Diamonds – both natural and synthetic – can be treated to improve their clarity and colour. Stones can be laser drilled to remove dark coloured inclusions, and surface reaching fractures can be filled with glass. Colour can be removed or changed by subjecting the diamond to different pressures and temperatures, or irradiated to add or alter colour. Diamonds can even be coated to change their appearance.


A diamond simulant should never be sold to you as a diamond. Anyone doing so would be breaking the law, and a reputable jeweller will be able to examine the stones they sell to be sure they are genuine diamonds. Larger diamonds are likely to accompanied by laboratory certification from somewhere like Anchorcert. The problem with simulants being sold as real diamonds other than the massive decrease in value, is their hardness and durability. The stones in a 20 year old cubic zirconia ring that has been worn daily will likely be in poor condition, while a diamond ring will more than likely look as good as new with a clean.

Synthetic diamonds are much harder to spot than simulants, and will need a very experienced gemologist or even laboratory testing to confirm. No one in the jewellery industry should be selling you a synthetic diamond (or any other gemstone) as natural – again, it does affect the stone’s value.

Jewellers also have a duty to tell you if the diamond has been treated. Glass fracture filling, for example, affects the structural integrity of the stone, and something as simple as cleaning the piece of jewellery or re-tipping a claw could damage the diamond irreparably. There is even some evidence that exposure to UV light can cause issues for filled diamonds.

So the advice for buying diamonds is no different to any other significant purchase: buy them from a reputable retailer/dealer who understands what they are selling and to whom there is recourse should you be sold something incorrectly. Diamonds are incredible, beautiful and mesmerising gemstones. Good quality diamond set jewellery will become an heirloom, an item of value to be passed down the through generations. A small and rare piece of the Earth, formed billions of years ago under the perfect set of conditions and something which invariably, we will run out of eventually.