Almost all diamonds form with inclusions. These may be small crystals of other minerals that become trapped in the diamond as it forms, or irregularities in the atomic structure of the diamond crystal. This may mean that you see small dark marks or white lines or wisps within the stone.

The clarity grade given to an individual diamond is an assessment of its relative freedom from inclusions (internal characteristics) and blemishes (external characteristics), with grades ranging from Flawless to Included. The grade is assessed by a trained diamond grader using 10x magnification and takes into consideration the number and type of inclusions, how large and how visible they are and their position within the stone. The standard grading system used internationally was developed by the Gemological Institute of America (GIA) and uses clear definitions for each grade so that it can be easily understood.

You may see some slight variations on this system when you are looking for a diamond. For instance, the ‘I’ grade is often referred to as Piqué with the grade given as P1, P2 or P3. Some grading bodies also use ‘Loupe Clean’ instead of Internally Flawless.

When choosing a diamond, it is important to remember that every stone must fit into one of the given grades. Diamonds are very rarely flawless, and the majority will have visible inclusions. Stones with particularly obvious inclusions are often not certificated, since it is not a selling point to have an I2 or I3 grade attached to the stone. This means that thousands of diamonds must every week be allocated to a very small number of grades, so each will cover a lot of variation. It is therefore important to know the detail of an individual stone’s clarity: what type of inclusions does it have and where are they situated within the stone?

The three diamonds pictured above are all graded as SI1, but there are significant differences between them, easily visible on these highly magnified images. In the image on the left you can see some white, ‘feather’ type inclusions towards the edge of the stone (imagine a clock face and look at 2 and 6). These would not be seen by the naked eye, and the centre of the stone is free from obvious inclusions even at the magnification used in the image. The centre stone is also mostly free from obvious inclusions, but in this case has a dark crystal inclusion right at the centre. This is much more likely to be seen than the off-centre white inclusions in the previous diamond. The right-hand stone has a few more inclusions, with several small, dark crystals scattered across the stone. All these combinations receive an SI1 grade, but they are very different in their overall appearance, and although they are the same weight, colour, clarity and cut grades, there is a few hundred pounds difference in price because of the subtle differences in the type and location of the inclusions. On paper the one with more inclusions may look a better buy because it is less money for the same grade, but there is a reason for the difference, and spending a little more can get you a more attractive stone.

While the variation in overall quality and price within each grade can be large, it is also often the case that the inclusions within a stone are so tiny that only a trained diamond grader will see them. The diamonds in the images above are graded, from left to right, VVS1, VS1 and SI1, but even at high magnification the differences between them are subtle. Therefore, a report from a trained, expert diamond grader is important; to the untrained eye the differences may not be visible, but the price can vary significantly.

We have diamonds in stock and available to view in our showroom that range in clarity from VVS to I grades, and our expert gemmologists and diamond graders can talk you through the differences and help you to make an informed choice. Most of our diamonds also come with GIA reports that give detail on their clarity, so you know exactly what you are getting. If you’d like to have a look before coming to see us, you can also view a large selection of our diamond rings online.