Buying Diamonds With Gemologist Nadine Aysoy

Diamonds are widely accepted as one of the best commodities you can invest in. Global diamond jewellery sales continue to grow, increasing three-fold in the past 25 years, and are currently worth in excess of US$72 billion every year. But only about 30% of diamonds are of gem quality and are distributed to experts for cutting, polishing and jewellery manufacture. The remaining 70% of diamonds are sold for industrial applications including cutting, drilling, grinding and polishing in industrial applications.

So how to buy diamonds and make sure that you invest in the best diamonds out there? We spoke to the certified Gemologist and jeweller Nadine Aysoy who we caught up with at the press presentation of her jewellery collection.

“I work with a lot of different stones and of course that includes diamonds that I use in abundance as pavage 0.1ct to 0.25ct extremely well cut to enhance the jewellery with fire and brilliance,” Commented Nadine showing her Tsarina earrings. She continued: “When I work with a larger stone 0.50 ct and above I always make sure to get it with its certificate from a reputable organisation. Be aware that certificates are not all equal and make sure to get it from the 3 most reputable labs.”

Hacks from Nadine Aysoy: How to Spot Fake Diamonds

“There are a few things you can do,” says Nadine. “You need to acquire a loop ( magnifying glass) and you can start by looking very closely:”

  1. If you see that the stone has absolutely no imperfections you should get suspicious. Diamonds are made in nature so you will see some imperfections in the carbon. If not it is a fake or a lab grown. You should consult a gemologist to make sure.
  2. The edges of the diamonds are always very sharp. If not and the edges are round it is not a diamond.
  3. Rub sandpaper against the stone. If it is a diamond it will not scratch! Diamonds are very hard and used in the industry for cutting. If it scratches it might be a a cubic zirconia or topaz.
  4. My favorite – the fog test. If you breathe on the stone and it fogs up for a moment like glass, it is not a diamond because diamonds don’t retain the heat.
  5. Then there is the reflection or sparkle which is grey and white, called the brilliance. It will reflect rainbow colours to other surfaces, it’s called fire. Fake diamonds will have the rainbow colour inside the stone!
  6. A diamond, if placed over a newspaper, will not show the black reflection of the paper. It will keep its brilliance and the light will scatter inside the diamond. A fake diamond will let the light go through and you might even be able to read the letters and words of the paper depending on the size and cut of the stone. The light passes through the stone.

Nadine Aysoy Jewellery featuring diamonds.

What Could be Used Instead of Diamonds?

White topaz, white sapphire, cubic zirconia, moissanite and lab-grown diamonds that are technically ‘real’diamonds because of the composition but at least 20 to 30% cheaper.

Diamond Cut

The cut can either increase or decrease the value of the precious stone. A good cut showcases the gemstone’s colour, diminishes its inclusions, and exhibits good overall symmetry and proportion. Because gemstone colour can vary, there are no hard, geometrical standards when it comes to maximizing the brilliance or colour.

Gemstones, especially rarer ones, are sometimes cut for size without regard for their colour. For example, when corundum varieties such as sapphire and ruby are cut for maximum weight rather than beauty, they may display banded colours or streaks. 

When buying, look at the gemstone in the setting and ensure that all facets are symmetrical. An asymmetrically-cut crown indicates a gemstone of low-quality. In all cases, a well-cut gemstone is symmetrical and reflects light evenly across the surface, and the polish is smooth, without any nicks or scratches. 

It is not rare to find too shallow or too deep diamond on the market. These are produced from the off cuts and are made to generate extra cash to the diamond cutters. As you might have guessed, they are less valuable and produce little to no sparkle. 

Always check the certificate for the cut. Expect to see only ‘Excellent’ in the Cut section of the certificate for established jewellers. Anything but – Very good, Good, Fair, Poor or Very poor – means you are dealing with the low-quality stones that can hardly be classed as an investment.


Gemologists use the term “inclusion” to define characteristics found inside a stone. Inclusions are often used as an indication that the gemstone is of natural origin, especially in case of colour stones. A “blemish” is a characteristic that affects the stone’s surface. All in all, stone clarity can be summarised in one simple table. 

The highest-grade stone will be Flawless. These stones are very rear. For grades IF through SI, clarity grade has an impact on the diamond’s value, not on the ‘naked eye’ appearance.

While Flawless or Internally Flawless diamonds are the rarest and most expensive, the VVS and VS quality diamonds are often used in accent stones and even more so in affordable class jewellery. 

Unfortunately, clarity is very difficult to judge accurately by an inexperienced consumer and thus the certificate will come with every luxury jewellery.

Diamond Carat Weight

Diamonds and other gemstones are weighed in metric carats: one carat is equal to 0.2 grams, about the same weight as a paperclip. The size of a 1 carat diamond is approximately 6.5mm – based on the assumption that the stone is cut to ideal proportions. On the other hand, the size of a .5 carat diamond is approximately 5.2mm. Even though the carat weight is 50% of a 1 carat stone, it doesn’t face up twice as small.

As with diamonds in the normal D-to-Z color range, large fancy color diamonds are rarer and more valuable than small ones.

Diamonds Colour

For white or colourless diamonds – as opposed to coloured diamonds – the diamond industry has adopted an alphabetical colour scale from D to Z, with D as the highest grading. As you go down the scale, the diamond starts to develop a yellow or brown tint.  Experts in the world of diamonds determine the colour by comparing a diamond against a master set of diamonds of different colours. Without comparing diamonds side by side, it is very difficult to see the difference between a D and a G.

Completely colourless diamonds (such as D and E) are much rarer than others which is why they come with a higher pricing premium. The key question is always where to draw the line when choosing the colour of a diamond – how far can you compromise colour before the diamond is too tinted? The answer to this question is relative to your budget and quality expectations.

Bear in mind that D-F diamonds should only be set in white gold/platinum. This is due to yellow gold giving a yellow hue to the diamond, which is not desirable in the case of D-F diamonds.

Fancy Diamonds

With fancy color diamonds—the ones outside the normal color range—the rarest and most valuable colors are saturated pinks, blues, and greens. In all cases, even very slight color differences can have a big impact on value.

Compared to fancy yellows and browns, diamonds with a noticeable hint of any other hue are considerably rarer. Even in light tones and weak saturation, as long as they show color in the face-up position, they qualify as fancy colors. Red, green, and blue diamonds with medium to dark tones and moderate saturations are extremely rare.


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