Summary: What is an Inclusion?
Inclusions are flaws either within the diamond itself or on the surface of a diamond which may or may not affect it's overall appearance.
Inclusions refer to the flaws found within diamonds, both natural and man-made. There are particular names for each of the inclusions, and knowing these will assist you tremendously in your quest for the attainment of the diamond that is ideal for you.
The geologic definition of inclusion is any foreign object, be it solid, liquid or gas, trapped within a rock or mineral. In the case of diamonds, this includes any kind of damage to the crystalline structure occurring within the diamond. This is the far more important category to be familiar with, as inclusions are the most difficult flaws to be overlooked or corrected. Inclusions can greatly affect the transmission of light within and through the diamond, depending on the size (as measured in microns) and placement of the particular inclusion or inclusions. It is important to remember, however, that all natural diamonds have inclusions, and that the only inclusions that professionals are concerned with are those seen at 10x magnification or less, as well as inclusions that threaten the stability of the stone.
- Feathers: Feathers are inclusions that resemble feathers in form, as though a feather were sitting within the diamond's structure. These can be fairly innocuous to the diamond if they are small enough. They can, however, become quite dangerous to the diamond if they reach the surface, where they can damage the integrity of the diamond, making the diamond prone to breakage. Indicated on the grading report as red lines.
- Pinpoints: This is one of the most common of inclusions. A pinpoint is a clear or white spot that occurs within the diamond during its formation. These are actually just tiny crystalline growths. That is to say, pinpoints are tiny diamond crystals within the diamond. These are very difficult to see, even by a professional, and are usually noted on a grading report as either, 'pinpoints not shown', or as tiny red dots.
- Carbons: Carbons are similar to pinpoints, but are dark in color, rather than white or clear. The name for this inclusion refers to small pinpoints of carbon, such as graphite, being trapped within the diamond crystal. This is a bit misleading, however, as most "carbons" are often minerals other than carbon. Such minerals include olivine, garnet, pyrite, silica, calcite, and iron oxides.
- Clouds: Clouds are groupings of pinpoints within the diamond. They are normally clear and so do not detract from the clarity of the diamond. However, a large cloud (simply a large group of pinpoints) that covers a large portion of the diamond's interior (a third or more), may damage the diamond's overall clarity. Clouds are indicated on a grading report as a series of red points, red circles or are noted in the comments.
- Twinning Wisps or Intergrowth: This refers to lines, or groupings of inclusions that have twisted together to form a single twinning line of inclusion. These are more commonly found in fancy cut diamonds, rather than rounds. They are formed as the crystal is growing, and normally appear as ribbon-like bands originating in the center of the diamond.
- Needles: Needles are named so as they resemble long, thin needles included within the diamond's structure. These are the result of thin threads of included crystal.
Additional inclusion descriptions can be found in the Advanced Section of this page.
Additional uncommon inclusions:
- Knots: A knot is a diamond crystal, essentially a far smaller diamond, which sits near or on the surface of the diamond. These particular inclusions can be problematic, in that as they are separate crystals, their growth pattern will differ, often significantly, from the lines of the host diamond. The result of this is that it is often difficult, if not impractical, for the diamond cutter to polish the knot away, due to the softness of the saw being used on the surface of the diamond. Knots can severely reduce the value of a diamond.
- Internal graining: Grain lines occur both internally and externally. Internal grain lines are naturally occurring lines that are found in all diamonds. They result from irregular crystallization growth within the diamond during the diamond's formation. If the growth lines are clear, they will not detract from the diamond's light properties. If they are colored or dark, they will cause the light transmission to suffer, thus lowering the diamond's overall clarity grade.
- Laser lines: These are man-made inclusions. They resemble trails of clear thread, and can often be difficult to see. They are the result of a laser being used to remove an inclusion spot, such as an included mineral.
- Bearding: Bearding is also known as Girdle Fringing. As both names imply, this inclusion resembles hair-like markings on the girdle of the diamond. This is the result of the cut and normally does not affect the light properties or the integrity of the diamond. Excessive bearding can be polished or cut away.
- Cleavage: Cleavage refers to cracks within the diamond. If these are small enough, and difficult to see from the table down, they usually have little effect on the transmission of light. A large cleavage, located at the right angle can, however, potentially cause the diamond to break should it be unnecessarily stressed.
- Cavities: Cavities are just what their name sounds like, holes within the surface of the diamond. These are usually the result of one of two distinct actions. The first is the result of polishing the diamond; the second is the result of cleavage or a blow to the diamond. As the diamond is being polished, should there be a separate crystal, or knot, which is polished away, it will often leave a hole as the entire crystal falls away. Feathering can also bring this about, should the feathering occur close to the surface and then break away, leaving a cleft-like cavity.
- Included crystals or minerals: An included mineral or crystal is simply a mineral or crystal that has been trapped within the crystalline structure of the diamond. This is one of the more interesting of inclusions. The very nature of this inclusion indicates that you could have a tiny diamond, or other precious gem, included within your diamond, which may appear black, white or grey.