Diamond Inclusions: Which Ones Are the Most Detrimental to a Stone’s V


Determining the purity of a diamond is understood as the systematic evaluation of the inclusions it has. In general, the inclusions that mark the degree of purity of a diamond are found in its interior, but sometimes external defects can also have an influence on their sales price, especially if they penetrate the stone, break the symmetry, impair the overall appearance, and cannot be eliminated by polishing. This Rare Carat article will explain more about the diamond inclusions that are most detrimental to their value. So, you should learn more at Rare Carat here.

How do experts look for inclusions?

Observing the inclusions of the diamond at the time of graduation of purity at ten times magnification is a business standard. Generally, in professional practice, a pocket magnifying glass is used to appreciate the purity of diamonds. In the laboratory, however, the determination is made with a binocular microscope under special lighting conditions.

It is very important to learn more at Rare Carat and know that the determination of the purity grade of diamonds is extremely rigorous. It is not possible to accurately determine the purity grade of a mounted diamond, as the mounting itself and the dirt that often accompanies it can mask quite significant flaws. When there is no choice but to make a determination of purity under these conditions, this should be clearly stated, and the purity should be stressed as a guideline only, a minimum of two possible grades should be given, and it should never be assured that it is a pure diamond. If you want to go deeper into these subjects, learn more at Rare Carat.

Without further ado, it is time to describe the most detrimental inclusions to a diamond’s value.


Feathering occurs when a small fracture appears within the diamond due to differences in heat and/or pressure during its formation. These small fractures or cracks look like a bird’s feather when seen from various angles. Small feathers can often be practically invisible; however, most feathers appear with distinctive white coloration. Some diamonds present greyish or brownish feathers on rare occasions.

Feathers per se are not too much of an issue. However, when the feathers are too long or too many following a single direction, that diamond is at risk of splitting. For this reason, diamonds with large feathers are considerably cheaper than diamonds with any other inclusion. Such diamonds have a great durability risk. However, not all feathers look entirely bad. As previously stated, in many cases feathers are invisible and can go unnoticed.

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Black spots

Black dots or negative crystals inside a diamond are a testament to their natural origin. These are areas where carbon, the element that constitutes diamonds, has not received the same amount of heat and pressure; therefore, it did not crystallize. If there are large black dots or if their concentration is too high, they can absorb and block the light going through the diamond. This means the diamond can lose scintillation and brilliance. In other words, it’ll become less transparent and opaquer to the eye, regardless of the polish.

However, since black inclusions do not compromise a diamond’s durability, it is still a reasonable idea to buy diamonds with black spots if their view is obscured, such as on the sides of certain cuts, or deep inside near the core of the diamond.


Cavities are slightly deep openings yet small in diameter. Cavities appear when a surface microcrystal falls off or gets forcibly removed during cutting and polishing. To completely remove a cavity from a diamond, further polishing or adjustments in the cut of the facet are necessary. This is generally far from ideal because this process implies reducing the weight of the gem. This is a solid reason why cutters prefer to sometimes leave cavities untouched, especially if the cavities are not present in the crown.

Final advice

In all circumstances, it is also very important that the stone is well-cleaned to verify the presence of inclusions. Cleaning should be done with a colorless cotton or nylon cloth, which does not shed fibers. If this is not sufficient, it can be washed in alcohol or toluene. In the laboratory, brushes or “picks” are used to remove the dust particles usually deposited on its surface.

It is very convenient to observe the stone first with the naked eye under good light, take a first look with a pocket magnifying glass, and finally go on to determine the degree of purity accurately with the stereoscopic magnifying glass.

Depending on the color of the diamond and placement of other inclusions, most of the latter do not affect greatly a stone’s value like the three aforementioned types. Surface-level scratches and some colored or well-placed inclusions can be remedied with a polish and/or can be disregarded once the diamond is mounted.