The 4 Cs of Diamond Quality
Colour
While many diamonds appear colourless, or white, they may actually have subtle yellow or brown tones that can be detected when comparing diamonds side by side. Colourless diamonds are the rarest and most valuable of all. Colour variations are a result of the natural forces (i.e., temperature, pressure, trace elements) at work during the formation of diamonds within the Earth. Because subtle colour variations dramatically affect the value of a diamond, a colour grading scale is used to categorize the shading differences from one diamond to the next.
There is now an internationally recognised colour grading scale which starts at D (colourless), and goes down to Z (light yellow). Each letter grade represents a range of colour and is a measure of how noticeable the colour is
| GIA colour grade | Description | Appearance |
|---|---|---|
| D E F |
Colourless | Stone looks absolutely clear, with no hint of colour to the eye in colour grading or mounted |
| G H I J |
Near Colourless | Some colour tint is visible during grading. Mounted in a setting, stone appears colourless. GHI colour diamonds are considered very nice diamonds for fine jewellery. |
| K L M |
Faint yellow | Yellow or grayish tint is obvious during colour grading. Mounted, this stone still shows a tint of colour. |
| N-Z | Light yellow | Obvious yellow or grayish colour |
| Z+ | Fancy | Bright, remarkable colour - usually blue, pink, yellow |
With colour you should also know a little about fluorescence.
Flourescence
Another characteristic that does not affect the colour grade of a diamond but is worth keeping in mind is fluorescence This characteristic refers to the diamond's ability to fluoresce under ultraviolet (UV) light. The most common source of UV is a black light. When exposed to UV light, many diamonds will give off a distinctive glowing blue colouration. Although fluorescence may be displayed in various colours, blue is the most common in diamonds. The fluorescence of a diamond is defined by its intensity as either None, Faint, Medium, Strong, or Very Strong.
Clarity
Clarity is an indication of a diamond's purity. Clarity is determined by a diamond's naturally occurring internal characteristics. These characteristics are sometimes not visible to the naked eye and they are what make each diamond unique. The characteristics, or inclusions, may look like crystals, feathers, clouds or dark spots and the quantity, size, and location of these inclusions does have an affect on a diamond's value. Diamonds with fewer and smaller inclusions generally are more brilliant, assuming that the colour and cut are the same.
The U.S. Federal Trade Commission has established the jewellery industry's standards for diamond clarity based on 10-power magnification. A diamond is graded by its relative departure from "flawless"--the complete absence of inclusions under 10x magnification.
Less than 1% of all diamonds ever found have had no inclusions and can be called flawless (FL) or internally flawless (IF). VVS diamonds are also extremely rare. VS diamonds are of superior quality and are used in extremely fine jewellery. This clarity grade becomes more important as the diamond size increases. A large percentage of jewellery is made with SI quality diamonds. These diamonds are perfect for diamond studs or multi-stone diamond earrings, rings and bracelets or as accents in gemstone rings. I quality diamonds are acceptable as well for diamond jewellery or as accents but the sparkle is reduced by the number and location of inclusions.
| Clarity Grade | Description | Appearance |
|---|---|---|
| F | Flawless | Clear stone, free of all flaws, even under 10x magnification |
| IF | Internally Flawless | No inclusions visible at 10x magnification |
| VVS1 | Very Very Slight Inclusion #1 | Tiny inclusions are extremely difficult to find, even under 10x magnification |
| VVS2 | Very Very Slight Inclusion #2 | Tiny inclusions are very difficult to find, even under 10x magnification |
| VS1 | Very Slight Inclusion #1 | Minor inclusions are difficult to see under 10 x magnification |
| VS2 | Very Slight Inclusion #2 | Minor inclusions are somewhat difficult to find under 10x magnification |
| SI1 | Slight Inclusion #1 | Inclusions are easy to see under 10x magnification. These diamonds are considered "eye clean". In larger diamonds very very small inclusions may be visible and still be classified as SI1. |
| SI2 | Slight Inclusion #2 | Inclusions and/or blemishes are easy to see at 10x. These diamonds are considered "eye clean". In larger diamonds very very small inclusions may be visible and still be classified as SI2. |
| I1 | Included #1 | Inclusions and/or blemishes are obvious and rather easy to see without magnification |
| I2 | Included #2 | Inclusions and/or blemishes are obvious and easy to see without magnification |
| I3 | Included #3 | Inclusions and blemishes that are obvious to the unaided eye |
Carat
Diamonds are measured in terms of weight, not size. The heavier the diamond, the greater the carat weight. Two diamonds of equal weight can have very different values, because the quality is still determined by the colour, clarity and cut. As diamonds increase in size, their cost tends to increase exponentially rather than arithmetically. Thus, a one-carat diamond can cost significantly more than a one-half carat diamond of equal quality. The weight of a diamond less than one carat in size may also be described in terms of "points". There are 100 "points" in 1 carat.
Cut
Diamonds mined from the earth look like tumbled gems or beach glass. To turn the diamond into a beautiful gem, the diamond is cut with precise facets, or tiny polished faces. There are 58 total facets on the round brilliant diamond: 33 facets are in the crown and table (largest facet) located above the girdle (the diamond's widest point), 24 facets in the pavilion and 1 facet at the bottom, or culet.
A well cut diamond will have an amazing brilliance and fire. This is caused by white light reflecting off the diamond's surfaces and the mirrored depths of the pavilion. The key to desirable fire and brilliance is proportion. Light striking a shallow cut diamond will fall out the other side and not reflect back to the top. Light striking a deep cut diamond will get lost in the pavilion and also be unable to reflect back to the top.
