The 4 c's of Diamonds - Part 3 of 5 - Clarity
Did you know that of all diamonds unearthed from mines a mere 20% is destined for use in fine jewellery and of them less than 1% is graded as flawless? Underground, during their crystallization, and on their way up, diamonds trap mineral impurities. Extreme pressure and heat often cause anomalies to their structure. These internal characteristics are called inclusions. Nature or human hand can also cause surface flaws; namely blemishes. Diamonds with the least visible defects receive the highest clarity rates and the chilliest price tag. Before shopping for the diamond of your dreams get to know what you are paying for. You may find our short video on Diamond grading helpful - click here to view.
History of grading
Clarity is one of the 4Cs of the diamond grading system of GIA (Gemological Institute of America) that was established in 1953 by the Richard T. Liddicoat team. Based on industry terminology and lastly revised in the 1990s, the current scale consists of eleven clarity grades: Flawless (FL), Internally Flawless (IF), Very Very Slightly Included 1 & 2 (VVSI & VVS2), Very Slightly Included 1 & 2 (VS1 & VS2), Slightly Included 1 & 2 (SI1 & SI2), and Included 1-3 (I1-3). Today, each GIA report for a-carat-and-over diamond contains its clarity plot or diagram which is mapping its imperfections, and is used as a reference.
Types of Imperfections
Inclusions are made of solids, liquids, or gases. Beyond actual minerals in any form, they can also be structural flaws. And they have interesting names such as pinpoints (tiny dot crystals), needles, cavities, knots (dark and visible), clouds (a cluster of pinpoints or crystals often causing haziness), feathers (internal cracks), and twinning wisps (a visible mix of different forms of inclusions). Crystals within a diamond can be white and blend in, while black carbon spots may be quite obvious. On the surface, blemishes appear as man-made polish lines, scratches, and chips, or natural nicks and pits (holes).
Image courtesy of Cape Diamonds, South Africa.
In the lab, the grader holds each cleaned diamond in tweezers and examines it under a 10x magnification loupe with darkfield illumination, from all angles as well as upside down, so that they detect every possible inclusion through the table and the other facets. They shift from darkfield to reflected overhead lighting to tell inclusions from blemishes, and they zoom to the diamond via a stereo microscope (although greater magnification doesn’t count in the overall grading). They also examine it with naked eye from a 15cm distance and if they can’t see any inclusions they describe it as ‘eye-clean’ (FL/IF, VVS 1, VVS2, and VS1). ‘IF’ diamonds have only microscopic blemishes. Skilled graders find it very hard to trace imperfections in the VVS ones and only a small percentage of VS2 are not eye-clean. SI1/SI2 are rarely and I1-3 are never eye-clean. ‘Included’ are not eligible for fine jewellery because their imperfections seriously affect the brilliance, clarity, and often integrity of the stone.
Inclusions visible under 10x magnification affect the grading of a diamond but not necessarily its beauty and desirability. In eye-clean diamonds you cannot see them. In those between VS2 and SI1, your choice depends on various factors. The size and number of the imperfections might lower the clarity grade. If a cloud is oriented in a way that inhibits light transmission, the stone appears less charming too. Inclusions located right under the top facet (table) or in the middle of the crown are often noticeable. If found below the crown facets, they might pass unnoticed. Inclusions near the edges or the pavilion might well be hidden by the setting of a diamond ring. Yet relatively ‘sheer’ internal cracks close to the surface might put the stone at risk of chipping or cracking. Finally, the colour of an inclusion is mostly preferred to be white rather dark and contrasting.
The extremely few customers who shop for flawless diamonds are willing to pay extra for the not-so-visible rarity of the stone. In real terms, you can be equally mesmerized by a less rare VS2 which is definitely value-for-money. Below that grade and up to SI1, everything should be judged on a gem-by-gem basis. The size and the shape of the stone will also define your choice. Opt for higher clarity grades in you need a larger or step-cut (Emerald, Asscher etc.) diamond. Large or rectangular facets especially those with a ‘mirror effect’ emphasize imperfections. Brilliant-cut round, oval, princess, pear ones disguise imperfections via impressive reflections.