How to Select a Beautiful Diamond

How to Select a Beautiful Diamond

The first basic "four C's" of Carat, Clarity, Colour and Cut will be enough to prepare you to shop for diamonds. Jewellery junkies and physicists might like to do the full tutorial.

You see, this tutorial is all about the way diamonds look. A diamonds appearance is mostly a result of the way it has been cut. I am known world over as the "Cut Nut" and I work tirelessly with leading researchers, diamond cutters and the heads of diamond grading labs, to improve a diamonds appearance.

When I first opened Precious Metals, in 1976, I was a young geologist. I was amazed that badly cut lifeless diamonds were often more valuable than sparkling beauties! I discovered Cut is the Cinderella of the 4 C's; most diamonds are 'Cut for Carats' not for beauty.
Even if you have no intention of shopping with Precious Metals, we hope you will learn to avoid some pitfalls, and buy a beautiful diamond. In the future the most beautiful diamonds will be worth the most money, and that is what our specialty.

Carat Weight

Carat is the simplest and most objective of the four C's. Pop a diamond on the scales, if it weighs .2 gm then it is a 1.00 carat diamond. 1/4ct is often called 25 points.

Everyone knows more Carat weight means more cost. But what comes as a surprise is that BIG diamonds are very rare; double the weight costs around 4 times more. And the magic 1.00ct weight D color Flawless costs 1.7times more than a 99 point or 0.99ct D Flawless.

So for diamond cutters, reducing the Carat weight to produce a smaller yielding Ideal Cut diamond is BAD for business. GIA surveyed 67,000 stones submitted for grading and found less than 3% were Ideal Cut.

But weight does not equal size! These two diamonds have the same diameter, and each could be cut from the rough diamond in the centre. The dull tone on the left weighs more, so it sells for more.

Even when diamond cutters produce so called Ideal Cuts, they usually can't resist leaving a little more weight on the crown and pavilion (the top and the bottom) to push the stone to the next 'magic weight'. This has a critical impact on a diamonds beauty. But at Precious Metals we screen these diamonds using our own invention; the Ideal-Scope™ . Not only do Precious Metals diamonds outshine all others, you don't pay for useless weight.

The magic weights are 1/2ct, 3/4ct, 90 points,1ct,1. 5ct, 2ct etc. 'Under-sizes' are diamonds that weigh just below a magic weight; they are rare in ideal cut stones, but we usually have some. Another way to tell if a diamond is well cut is with the Holloway Cut Adviser which also takes the spread of a diamond into account.

The girdle or edge thickness is also important. If a diamond has no girdle, or it is extremely thin, the diamond can chip easily. Medium to slightly thick is best, but thicker girdles add extra weight for no benefit and more cost.

Cut

Cutting transforms a diamond pebble into a sparkling gem. It is said that 98% a diamond's life and sparkle comes from its Cut! But unlike Carat - Cut is complex and the least understood of he 4 C's. The industries peak standards body, the Gemological Institute of America (GIA) has no grading standard for the quality of a diamonds Cut. Why? Because the jury is still out. My training as a geologist helped me understand what makes a diamond beautiful. In 1984 I wrote a thesis on the Firescope ™ and then 8 years later I had an opportunity to apply my theories when I began to buy blind, unseen diamonds direct from overseas cutters (via a B2B site). I refined my study and established my own Ideal cut proportion standard. This enabled Precious Metals to cut out the middle-men and sell the most beautiful diamonds at better prices.

Deep Cut

The bottom left picture shows a diamond that is cut too deeply and light is leaking out the back. This is seen as white in the Ideal-scope ™ image; the diamond looks dull and drab and has a smaller spread . Ideal cut diamonds, as seen bottom right, look red (with a star shaped black pattern).

Ideal Cut

Colour

Most diamonds have a hint of yellow or brown. The rarest and most expensive colourless diamonds are D or Icy white - on a scale that goes to Z and is yellowish. (More colour than Z is graded as a 'fancy' colour). At Precious Metals all our diamonds are D to H and we advise you buy a diamond in that range because most people can easily detect the "off colour" in I and lower grades. However if you want the very best then we recommend icy white D to F "collection colours" as they are known in the trade. However some people actually like the "warmth" of I ,J or K colours. But the main reason people buy a lower Colour is simply to trade up in one of the other 4 C's. For instance in Asia, low Clarity is synonymous with 'impure' and so Colour is often traded off for a higher Clarity. I find about half the people in a blind "Pepsi" taste test can tell the difference between a D and an H coloured diamond; at I and lower, the majority of people can see the faint tint of yellow. Colour has a bigger impact on price as the clarity and carat weight goes up.

Glassy looking cuts like Asscher and emerald cut diamonds show more colour than ideal cut rounds; brighter cuts face up more colourless. Now for something odd: It is easier to see the colour of a diamond in a white setting (platinum or white gold). If you have a yellowish diamond, then setting it in a rubbed over yellow gold bezel style setting can improve the apparent colour by a couple of grades. Fluorescent diamonds with a bluish tint (about 30% of diamonds) usually appear more colourless.

Clarity

After carat weight, clarity has the biggest impact on diamond prices. Diamond Clarity is symbolic of "purity" – the more flaws, the less valuable the diamond, but unlike emeralds, inclusions in diamonds are rarely "flaws" that result in breakage.

Imperfect - I (Pique - P)

Medium clarity diamonds are just as brilliant as Flawless diamonds; even experts can not tell the difference between Flawless and SI1 diamonds without a loupe. SI2 is supposedly the borderline where inclusions become visible to your naked eye. If you can see an inclusion with your naked eye in normal light, from 14 inches (35cm) without having previously identified its position using magnification, then the stone is 'I' for Imperfect or the European term – ' P' for Pique (PeeKay). However some young people with excellent eyesight may be able to spot a VS2 inclusion.

Precious Metals only stock diamonds in SI2 to Flawless, but we recommend SI1 and VS2 as being the best balance for quality and value.

Slightly Included - SI

Giving a grade based on inclusion quantity, size, placement and type is difficult; graders are human . Diamond grading reports are meant to resolve arguments between buyers and sellers, but ultimately they are just "expert opinions" under 10 times magnification with a loupe. Even GIA has given different grades for the same resubmitted stone.

Very Slight - VS

EGL and EGL-USA introduced an SI3 grade in 1992. SI3 has been used in the dealer market for many years because of the big price difference between I1 and SI2. The World Federation of Diamond Bourses wants all labs to introduce SI3, but most refuse. Since 1992, most labs have softened their SI2 grades.

Very, Very Slight - VVS

Grading reports include plots of inclusions (marked in red for internal and green for external features) and this is useful for identification. Often only the main "grade makers" are plotted, and additional inclusions are listed in comments: "pin points not shown" etc. A common comment is "Clouds Not Shown"; a cloud drawn on plots look so bad that no one would buy the diamond. Clouds are only a problem on SI1 and lower clarity's if no other inclusion is marked on the plot, i.e. the cloud is the grade maker; a big cloud may dull the diamond. It is rare for even I1 diamonds to be dulled by inclusions.

Diamonds with SI1 (left) and I1 (right) Clarity, 10x magnification.