Diamond Lessons

It is useful to understand the anatomy of the diamond. Like a human body, each part of the diamond has a specific name, and knowing these, and having a working understanding of what each part contributes to the diamond as a whole, will help to assist you in purchasing a beautiful diamond.

There are eight basic parts in the diamond anatomy. These are: Facets, Table, Diameter, Crown, Pavilion, Girdle, Depth and Culet.

Facets

These are the flat planes that form the outer face of the diamond. Each facet is angled, shaped and cut in order to produce a particular light effect for the diamond and to most effectively reflect the inner crystalline structure of the diamond. The facets are designed to allow light to reflect off of, enter into, pass through and exit the diamond. The arrangement of the facets is designed to allow light to enter (normally through the table), refract within the diamond itself (producing its "fire"), to exit the diamond (again, through its table) as well as reflecting light directly off of the diamond's surface.

Table

The largest facet of the diamond. This is the facet that sits at the top of the diamond, and serves as the main entrance and exit point for light.

Diameter

The measurement of the width of the diamond at its widest point (girdle).

Crown

The crown refers to the part of the diamond from the girdle up. This means that the section of the diamond from the widest point to the top, or table, of the diamond is the named the crown.

Pavilion

The pavilion is the counterpoint of the crown in that it is the bottom portion of the diamond. From the girdle, or widest section, of the diamond to the bottom (or culet) is referred to as the pavilion.

Girdle

The girdle of the diamond is the name for the widest portion of the diamond. The diamond's diameter is measured at its girdle. The common practice today is to facet the girdle itself, although these facets are not included in the diamond's final facet count. As long as the girdle is not described as extremely or extra thin or thick the girdle has no effect on the stability of the diamond.

Depth

A diamond's depth is the measured height of the entire diamond. Measuring from the top of the diamond (the table) to the bottom of the diamond (the culet), the depth of the diamond helps to set the ratios for the rest of the diamond's cut.

Culet

The culet is the bottom of the diamond and the diamond's smallest facet. The culet has tremendous effect on the rest of the diamond in that a properly formed culet will allow the light that has entered the diamond to most effectively exit through the diamond's table and re-enter the eye. A culet that is cut too large can cause a detrimental effect in the diamond's light display. The overly large culet can cause the light to leak out from it, thus causing the diamond to appear to have a hole within it. The culet needs to be small enough, and within the correct ratio to the rest of the diamond's anatomy to allow the light to reach it and be refracted back within the diamond and reflected back out of it. It is not uncommon for a diamond to have no culet, and instead have the pavilion come to a point. There is no right or wrong to having or not having a culet.

Light Leakage

The term light leakage refers to the loss of light within the diamond. When properly cut, a diamond will exhibit fire (resulting from the proper cut of the crown), brilliance (resulting from the proper cut of the pavilion), and scintillation (resulting from the proper placement, or symmetry and alignment of a diamond's facets). Scintillation is the actual play of light within the diamond itself. Should any of the elements involved be cut incorrectly, resulting in poor symmetry, poor brilliance, poor fire or a combination of the three, light will exit the stone at one of the sides, rather than reflect and refract within the stone, exiting through the table.

Facet Shapes and Descriptions

Bezel

The bezel facet is the name for 8 kite-like facets that are cut into the crown of a brilliant round cut diamond.

Kite

This is a facet that has been angled with four sides so as to best create the brilliance and luster of diamond. This type of facet is most commonly associated with the brilliant cut of diamond.

Rectangular

The next common type of facet is the long rectangular facet. This long facet is the facet that one sees when looking at a step-cut diamond, such as an emerald cut. The long, wide plane created by the use of the rectangular facet allows for a warm glowing play of light in and on the diamond.

Star

The star facet is a triangular facet. There are 8 of these facets on a brilliant cut diamond and they are found on the upper crown.

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.

Inclusions:

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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:

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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.

Blemishes are flaws that are found on the surface of the diamond. These are not usually as damaging to a diamond's clarity grade as inclusions, as many blemishes can be polished away prior to the grading. This type of flaw can be formed as either a natural part of the diamond's growth or as a result of the cutting and polishing process. Knowing the names of different blemishes, and being familiar with their descriptions and definitions will afford you a greater ability to differentiate between diamonds with blemishes that are potentially damaging to the light transmission qualities of the diamond, and diamonds that have innocuous blemishes.

1. Polishing Lines: Polishing lines arise during the cutting process of the diamond. In form they appear as grooves or scratches, usually running in parallel lines on the facet or facets of the diamond surface. These lines can be negligible in regards to the overall clarity and grade of the diamond if they are quite small and if found on the pavilion.
2. Naturals: Naturals are flaws that are not always considered flaws. They are small portions of the original rough diamond's surface that are left unfinished or unpolished by the cutter. While this might seem odd, it is normally done in order to save diamond weight during the cutting process, and also serves as indication of the skill of the cutter. These are normally found on the diamond's girdle and do not detract from the diamond's clarity grade if they do not overly extend or expand the diamond's girdle.
3. Trigons: Trigons are raised triangular shapes that are found on the surface of a diamond. The triangular shape is the result of the octahedral crystalline structure that makes up a diamond, as the face of the octahedral form is a triangle. These can be formed as a natural growth of the crystalline structure, but can also be formed during the cutting and polishing process.
4. Pits: Pits can be some of the more problematic of blemishes. Pits are tiny holes, often appearing as white dots, appearing on the surface of the diamond. The location of the pits is critical to its impact on the grade of the diamond. Should the pits appear on the table of the diamond, they can be detrimental to the light qualities, and so precipitously lower the diamond's grade. Smaller pits can be polished away, but larger pits occurring on the diamond's table may require re-cutting the table, causing the diamond to lose some of its weight.
5. Scratches: Scratches are simply that, scratches on the surface of the diamond. These are not unusual and can appear as thin, white lines, shallow in depth and narrow in width. Scratches can detract from a diamond's grade, but scratches can usually be polished away. It is important to be aware, however, that while a diamond can be re-polished to its original shine, it must be removed from its setting in order to allow for the re-polishing process.
6. Nicks: Nicks are small areas of the diamond where an impact has caused a tiny portion of the diamond to break away. These are most often found on the diamond's girdle, as the girdle is the most extended and at-risk part of the diamond. Nicks can be polished out through the polishing down of a new facet. It is important to note that while this can solve the problem of a small nick, too many additional facets will negatively affect the appearance and light qualities of a diamond.