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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% adiamonds life and sparkle comes from its Cut! But unlike Carat - Cut is complex and the

least understood of he 4 Cs. 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 TM 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 proportionstandard. This enabled Precious Metals to cut out the middle-men and sell the most

beautiful diamonds at better prices.

The bottom left picture shows a diamond that is cut too deeply and light is leaking out theback. This is seen as white in the Ideal-scope TM 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).

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 colourthan 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 collectioncolours 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 Cs. Forinstance in Asia, low Clarity is synonymous with impure and so Colour is often tradedoff 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.

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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 rubbedover 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 issymbolic of purity - the more flaws, the less valuable the diamond, but unlike

emeralds, inclusions in diamonds are rarely flaws that result in breakage.

Medium clarity diamonds are just as brilliant as Flawless diamonds; even experts can nottell 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 aninclusion 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 excellenteyesight 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.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 andsellers, but ultimately they are just expert opinions under 10 times magnification with aloupe. Even GIA has given different grades for the same resubmitted stone.

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. Since1992, most labs have softened their SI2 grades.

Grading reports include plots of inclusions (marked in red for internal and green forexternal 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 noone would buy the diamond. Clouds are only a problem on SI1 and lower claritys 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.