Determining the clarity of a diamond
Diamonds are commonly graded according to “The 4 C’s”; these are Colour, Cut, Carat and Clarity.
Clarity refers to the degree of purity if the diamond, specifically whether or not there are “flaws” in the diamond. A diamond of high clarity will have few or no “flaws”, a diamond of low clarity will have many.
The overall name name for what we call “flaws”, “inclusions”, “crystals”, “feathers”, plus all of the other terms relating to clarity grade is “clarity characteristics”. This is because they are not always bad things; they can help to identify the diamond, and also because they sometimes add to the interest of beauty of the diamond (for example, coloured mineral inclusions can be extremely beautiful).
Clarity grading is done with a lens of 10x power, called a “loupe” in the diamond business. Binocular microscopes of up to 60x magnification are useful to determine the nature of a inclusion, but higher magnifications are not used to determine clarity grade.
When grading the clarity of a diamond, it is important to consider all clarity characteristics under 5 categories: size, nature, colour, relief, position.
Quite simply, the bigger the inclusions in the diamond, the worse the clarity grade of the diamond.
You must consider what type of characteristic you are looking at, and its impact on the overall appearance on the diamond. An included crystal, or break will have more of an effect on a diamond’s appearance than slight graining, a cloud or a cluster of pinpoints.
Some inclusions are transparent or translucent, and as such will have less impact on the clarity grade than an opaque inclusion.
This is similar to colour, but links in to the background against which the clarity characteristic is viewed. White graining against a reflecting facet will be almost invisible, while the same graining against a non-reflecting facet will appear much more obvious, and could result in a worse clarity grade.
A large included crystal positioned to the edge of the diamond will be less easy to spot than a crystal of the same size, nature, colour and relief positioned in the centre of the diamond, and can therefore have a better clarity grade.
The scale used to measure clarity is the following:
Flawless – the highest purity, a flawless diamond will have no clarity characteristics under 10x magnification.
Internally flawless – similar to flawless, an internally flawless diamond will have no internal clarity characteristics, but may have minor negligible surface blemishes, not visible from the top of the diamond. (Often on the edge of the diamond.)
Very very slightly included, grade 1 and 2 (VVS1 and VVS2) – These diamonds will have clarity characteristics that are difficult to see under 10x magnification, even to a trained grader.
Very slightly included, grade 1 and 2 (VS1 and VS2) – These diamonds will have clarity characteristics which a trained grader will be able to find easily enough with a 10x lens.
Slightly included, grade 1 and 2 (SI1 and SI2) – These diamonds will have clarity characteristics which an untrained grader will be able to find easily enough with a 10x lens. Generally these should be invisible to the naked eye, but some SI2 grade diamonds have clarity characteristics visible to the naked eye.
Included (I) – These diamonds will have clarity characteristics easily visible to the naked eye.