Last updated on April 21, 2021
Diamonds are rarely perfect and usually have imperfections called inclusions or blemishes. While some types of blemishes affect only the appearance, others can be harmful to the structure of the stone. So what diamond inclusions to avoid?
What Are Diamond Inclusions?
Diamond inclusions, also known as flaws, are natural birthmarks that develop when a stone is formed in the earth’s mantle layer typically at depth of over 140 kilometres.
Since diamonds form under extreme heat conditions (at least 1050° Celsius) and their growth takes between one to three billion years, only rare diamonds emerge in flawless condition. Most of them are imperfect and contain different types of inclusions, which affect a diamond’s appearance, internal structure, clarity grade and price as a result.
Depending on their nature, diamond imperfections are classified into internal and external flaws.
Internal diamond flaws include crystals, pinpoints and clouds, needles, knots, graining, feathers or cleavages, twinning wisps, bearding and cavities. These flaws can be either minor or serious, depending on the way light travels within the stone.
External flaws, also known as blemishes, include scratches, extra facets, fractures, fingerprints, pits, nicks, naturals, carbons and chips. Sometimes these flaws can be polished down or can be cut to remove.
Depending on their size, nature and quantity, diamond inclusions may or may not be visible to the naked eye, but they are always visible to a skilled grader under 10x magnification.
What Diamond Inclusions to Avoid
Diamond chips are small, shallow openings on the surface of a diamond. They are often caused by wear and tear or accidental hits. Chips can be easily seen with a naked eye; however, the issue with them is not only visual.
Once the structural integrity of the stone has been damaged, there is a higher risk of the chip growing and spreading if subjected to further impacts. Needless to say that chips lower the value of the stone, and such diamonds are usually priced at a discount.
When buying a diamond, make sure to inspect it with a loupe and feel its surface and edges with your finger for irregularities. Be especially careful when buying used jewellery as the diamonds in it are more likely to have chips. Always look at the diamonds you are about to buy when they are taken out of their settings since they may conceal some of their defects.
In case you have a chipped diamond, you can get rid of the chip by having the stone re-cut by a professional diamond cutter. The cutter will remove some material from all sides of the stone until the chip disappears. Of course, the diamond’s carat weight will go down, but this way you can be sure the chip will not spread.
Dark Crystals or Black Dots
A crystal is a diamond or other material in its natural raw form that is embedded within the stone. Crystals are often colourless or various shades of white, however, they can be any colour.
Dark crystals or black dots are simply areas where carbon has not crystallized. If there are too many large black dots, they will stand out and detract from the visual appeal of the stone. Apart from being an optical flaw, black dots do not present any real danger to the structure of diamonds.
In general, you should avoid such stones as dark crystals can block the light entering the stone, resulting in less fire brilliance and scintillation. However, in case you are choosing among lower clarity diamonds that have black spots, you can opt for a stone whose dots are concentrated in places where they will not be that visible, such as sides or deep inside the stone.
A feather is a small fracture within a diamond’s internal structure. Depending on your viewing angle, a feather can be almost invisible or catch on light and look like a small white feather within a diamond. Rarely feathers may also have a grey and brownish colour, and they are noticeable to the naked eye.
Long feathers can cause durability issues, especially if they reach the surface or the girdle. If a diamond has long feathers, it is more vulnerable to stress, and in case of a hard hit, it may split along the fractures.
Diamonds with large fractures usually have low clarity grade and are much cheaper than stones of higher quality. However, paying less money for such a stone is hardly worth the risk of ending up with a broken diamond in the future.
It is fair to say that not all feather inclusions look bad. For example, if you are buying a diamond in VS or VVS clarity range, feathers may not cause any issues; however, they should be evaluated on a case-by-case basis.
A cavity inclusion is a small, slightly deep curved area typically caused when a crystal near the diamond’s surface is removed during the cutting or polishing process. In other words, you can think of a cavity as a hole on the diamond’s surface.
These cavities can be removed during the polishing process, but to completely remove a cavity inclusion from a diamond’s surface, a cutter needs to recut or repolish the diamond, which results in a weight loss. That is why cutters prefer to retain higher weight at the expense of a lower clarity grade.
Such inclusions accumulate dirt and oil and become darker and more visible with time. Moreover, if the cavity is large enough, it poses durability risks, so it is better to avoid such stones.