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Visual Clues: Is it a Diamond or a Fake?

The global jewelry market in 2018 had an estimated value of US$87 billion and is forecasted to grow to US$173 billion by 2035. That is a lot of jewelry and much of it features diamonds. But not everyone can afford diamonds and not all jewelry manufacturers choose to use diamonds in their designs. So how do manufacturers create pieces that give consumers the bling they want at prices they can afford? They use stones that look like diamonds but are not diamonds, these are called simulants or imitations. Simulants are not used to intentionally deceive people, they are used to resemble the look of diamonds without the associated price tags. Although we’ve all heard the stories of celebrity couples that go through contentious divorces, only to discover and reveal that the huge rock in their engagement ring turned out to be a fake. (sorry Lala ????) So if all these imitations are not diamonds, then what exactly are they?

Before we talk specifically about diamond simulants you need to first understand what the properties of diamonds are that make them so beautiful and the properties that differentiate them from the simulants out there? If you are looking at a diamond what do you see? It is important for you to know that gemologists are trained to never make sight identifications of any gemstone. Definitive IDs can only be made through standard gemological tests. For the purposes of this article, I will give you a few visual clues that may be tip-offs that what you are looking at may not be an earth-mined diamond.

1. Diamond is the hardest substance known to man-which means the surface will take a high polish creating a super smooth surface that has a high luster (adamantine) that reflects white light (brilliance) and produces silver flashes (scintillation.)

Gemologists define Hardness as a gem’s ability to resist scratching and Toughness as a gem’s ability to resist breaking or chipping. Both of these definitions are important when comparing diamonds to diamond simulants. Hardness is measured on the non-linear Moh’s scale, gem materials are ranked 1-10; diamond is ranked 10, alone at the top of the scale. Diamond is actually 140 times harder than the next lower material on the scale, e.g. sapphire, which measures 9. What people are very surprised to hear, is that diamonds are not the toughest gem material (that would be Jade) so it’s possible to chip or even break a diamond.

2. Well-cut diamonds have the ability to bend white light that enters the stone and break it up into its spectral colors as it exits, this is called dispersion, or fire.

Spectral Colors

The Most Common Diamond Look-alikes

There are two types of diamond simulants: Gem materials that look like diamonds: e.g. Crystal quartz, white sapphires, white spinel, zircon, and man-made imitations: e.g. glass, synthetic spinel, synthetic sapphire, crystals, and older synthetics that are rarely seen today, such as YAG and GGG.

The two most often encountered diamond look alikes are Cubic Zirconium (CZ) and Moissanite, which we will look at today. We will also provide a brief overview of man-made diamonds. These are diamonds in every sense of the word except they are produced in laboratories, at much more affordable prices. But more about these later, let’s look first at CZs and Moissanite.


Cubic Zirconium (CZ)

If you conducted a survey asking people which diamond simulants they are aware of, cubic zirconia would probably be mentioned most often. Like all simulants, CZs are transparent and near-colorless or colorless, although they are not color graded by gemological laboratories. CZs rank 8.5 on the Moh’s scale, and will stand up well to everyday wear but can be scratched. These scratches or abrasions may be visible along the edges of the facets. CZs have slightly higher levels of dispersion than diamonds, but this is difficult to discern by an untrained eye. Loose stones will feel heavier than the same size diamonds. They will also be completely colorless, whereby most diamonds have body-color, those that grade G-Z on the Gemological Institute of America’s (GIA) color grading scale. CZs are also without internal characteristics (flaws) and mined diamonds graded Flawless or Internally Flawless on the GIA scale are extremely rare.

A standard tool used by jewelers to separate diamonds from simulants is a diamond thermal tester. These instruments measure thermal conductivity, diamond is an excellent conductor of heat; other simulants are not. The tool quickly identifies diamonds and is reliable for most simulants. CZs are poor at conducting heat.

Synthetic Moissanite

Moissanite is a mineral that occurs very rarely in nature but is created in laboratories for commercial purposes, so its proper name is synthetic moissanite. Its hardness is close to 9 on the Moh’s scale, so quite suitable for everyday wear, but will after time show scratches and abrasions. It has much higher dispersion and brilliance than diamond, which is a sure tip-off, there is too much color radiating from the stone. For this reason, they are sometimes called “disco balls”

The body color may be near colorless to slightly yellow, from D-K if graded on the GIA scale and VS, and very slightly included on the clarity grading scale, but keep in mind they are never graded in a gem lab. Although Moissanite is a good conductor of heat (but not rated excellent like diamonds) it may fool standard diamond testers; however, there are special testers available specifically for Moissanite.


Lab-created Diamonds

This is the category that most confuses consumers. Man-made diamonds are produced in laboratories and feature the identical
optical (look exactly the same and handle light in the same manner) physical (same weight, density) chemical properties (pure carbon) as earth-mined diamonds.

Man-made diamonds have been around since scientists were first able to duplicate the process in laboratories in the 1950s. They expose pure carbon to the same heat and pressure conditions that occur more than 100 miles deep within the earth. But these were industrial-grade diamonds, needed to fill the huge demand, for use in everything from dental drills to diamond windows in X-ray machines. They are small, heavily included, black or brown, and not at all suitable for commercial purposes.

Over the decades, processes have evolved and improved and beautiful, large man-made diamonds are found more and more in jewelry stores today; however, they must be clearly labeled and sold as such. GIA has been grading laboratory-grown diamonds since 2007. GIA laboratory-grown Diamond Reports and identification reports document the standard GIA color, clarity and cut grade of the lab-grown diamond being graded.

These diamonds are environmentally friendly and ethically sourced, providing peace of mind to those with concerns about these issues. In addition, the price is approximately one-third to one-half the cost of comparable mined diamonds.

As you can imagine, it is almost impossible to discern if a diamond is lab-grown or mined simply by looking at it. Even trained gemologists struggle to do so using gem microscopes. Only with advanced equipment are highly trained specialists able to rise to the challenge and definitively make the call.




How can you tell if a stone diamond or an impostor? Well, as you can see there are a few visual tip-offs when it comes to imitations. But if you have a piece of jewelry that you are unsure of, take it to a qualified jewelry appraiser and they will be able to help you.

If you are interested in learning more about man-made diamonds click Here

I would love to hear your thoughts on simulants and lab-grown diamonds. What is your preference?

Thank you for reading my article!

Francesca de Granville, G.G., F.G.A.

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