Flaws in diamonds are morphological imperfections (inclusions, stripes, spots, cracks), as well as defects that arise as a result of its cutting. The process of diamond crystallization occurs under the influence of pressure and temperature, the difference of which can leave stripes and irregularities on the stone. You shouldn’t be afraid of all defects because they are the confirmation of the stone authenticity! 


Impact of Defects on Diamond Clarity

The clarity of a diamond determines the degree of visibility of internal/external defects in the stone. It is on the purity of a diamond that its durability and, of course, the final cost depend.

Internal Defects

These are natural imperfections that go deep into the stone but can also appear on its surface.

They are divided into:

  • “aesthetic” defects that only affect the appearance of the stone;
  • deep flaws that threaten the integrity of the stone.

Crystalline or Mineral Inclusions


These are particles of other minerals that are located inside the diamond. Inclusions can be microscopic, colorless, or colored. Large particles make it possible to recognize which mineral is inside (olivine, rutile, spinel) and are called crystalline. The edge on which the inclusion appears is hard to polish.


Structural Defects

They are single clusters of tiny dots that consist of voids or impurities. More concentrated ones create a white haze and reduce the clarity of the diamond. Structural imperfections also include deformations in the form of parallel stripes and seams.

Attention! The most dangerous structural defects are cracks or splits, especially when such a line reaches the stone surface. If the diamond is strongly exposed, it can crack! But, for example, you shouldn’t be afraid of black dots on the surface of a diamond. They only spoil the appearance of the stone but don’t pose a danger to its structure. They are least visible on the sides of the stone. Avoid diamonds with such inclusions closer to the top.


Pressure Cracks

They arise as a result of the unequal thermal effect of an included allophylian crystal.

Cleavage Cracks

They always run straight, parallel to each other in a particular direction. Along cleavage cracks, a diamond can easily crack upon mechanical stress.

Fracture Cracks

These are cracks that run chaotically in all other directions.


Such cracks in the light resemble a white feather. The longevity of a diamond is usually only affected by the deep feathers that reach the stone surface.

Twin Planes (Seams)

These are lines in the form of parallel stripes located on the bottom of the diamond. They appear when two diamond crystals grow together. Twin planes are usually colorless, less often with a yellowish tinge.


External Defects

These are the imperfections that appear on the surface of the cut. There are three types of them:

  • natural imperfections;
  • flows arising in the process of stone cutting;
  • defects that were formed during mechanical damage.

Natural Facets of the Crystal

These are the facets of the original diamond that remain after the stone has been cut. They are usually not recognized when viewed from above.

Notches and Breaks

Porous particles/incisions on the stone that occur under mechanical stress. 

Fringe on the Girdle

Small abrasions and cracks that extend into the stone over a short distance are called girdle’s “beard.” They appear during roughing of the diamond and negatively affect the clarity of the diamond.

Growth Lines

These are heterogeneities in the stone structure in the form of thin lines that arise during the formation of a diamond. They are invisible even from close range.

Twin Lines and Plates

These are the seams that appear on the surface of a diamond when two crystals are spliced. Since these planes are colorless, they are visible only as thin seams.

Grinding and Polishing Marks

These operations are carried out using a diamond paste, while the direction of movement of the polishing disc must be carefully verified. Otherwise, on the surface of the facet of the diamond, stripes and strokes will appear.

Figures From Impact and Damage

They are formed on the stone surface in the form of small spots and scratches of various sizes. While the latter are only on the surface, they are viewed as external imperfections.

Additional Facets

The cutter leaves natural facets under the girdle after the initial cutting or after grinding small defects. Additional facets don’t affect the stone’s brilliance and are a confirmation of the diamond’s authenticity.

Laser Needles

These are white channels that form when laser drilling a diamond. They are generally relatively straight with a small diameter.

Burn Marks

They appear when the stone overheats during polishing and can be removed by re-polishing, which will slightly reduce the weight of the stone.


These are small knotty irregularities on a polished diamond. They are formed from inclusions that reach the surface of the stone from the depths.