Crown: This is the entire upper part of the diamond above the girdle.  It consists of the table surrounded by the main upper facet, star facet and upper girdle facet.  This is where you will see most of the brilliance in a diamond.

Girdle: This is the outer edge of the diamond.  It is the band that separates the crown from the pavilion.  The girdle can have one of three different types of finishes depending on the cutter... bruted, faceted or polished. 

Pavilion: This is the bottom part of the diamond below the girdle.  It consists of the lower main facets, lower girdle facets and the culet.  The height of the pavilion contributes to the brilliance of the diamond.  If the pavilion is too shallow or too deep, light entering the diamond will be lost through the bottom.

Facets are the smooth flat surface of the diamond.  It allows light to enter, reflect and exit the diamond creating the beautiful colors seen in diamonds.

Table: This is the flat facet on the top of the diamond.  It is the largest facet on the cut of any diamond and is usually oriented on top facing the viewer.  This is your main window into the beauty that makes a diamond.

Star Facet: Sharing a side with the table, these 8 facets are called Star facets.  This is because when the diamond is seen from the top, these eight facets appear like a star

Bezel Facet: This facet, also known as a kite facet because they look like a kite, extend from the table to the girdle.

Upper Girdle Facet: These facets join the kite facet with the girdle. There are two highlighted in the illustration.  They are simply mirror images of each other.

Lower Girdle Facet: These facets join the pavilion facet to the girdle.  There are two highlighted in the illustration.  They are simply mirror images of each other.

Pavilion Facet: This elongated kite shaped facet on the underside of the diamond connects to the girdle at a point to the culet.

Culet: This is the point at the bottom of the diamond.  It is sometimes polished as a flat facet to protect the diamond from  chipping while the other facets are polished or when the diamond is being mounted in jewelry.  More often, the culet is 'closed' to a point eliminating its visibility.  If the culet is cut too large, it acts like a window through the diamond and can be mistaken for an inclusion.

All diamonds, no matter if it is an uncut diamond or a finished diamond ready for sale, has to be measured.  This section will teach you how diamonds are measured and what all the numbers mean.

Girdle Diameter: Also called the Diamond Width, this is the diameter of the girdle in a round diamond.  Since not all round diamonds are perfectly round, a Diamond Grading report will display a range.  This is done by taking the measurements from at least 4 different points and listing the smallest and the largest numbers in the report.  For example, a report may say 6.24mm-6.26mmx3.70mm.  The diameter ranges from 6.23mm at its smallest and 6.26mm at its widest.  3.70mm is the total depth of the diamond.

Table Width: This is the size of the table taken at its widest point.  Non-round shapes such as pears use the smallest diameter (width as opposed to length).

Crown Height Percentage: This is calculated by dividing the crown height with girdle diameter.  The crown height of the diamond is measured from the table to the girdle.  For example, if the crown height is 1.01mm and the girdle diameter is 6.25mm, the calculation would be 1.01/6,25=0.162 = 16.2%, perfect for an ideal cut.

Pavilion Depth Percentage: This is calculated by dividing the pavilion height with the girdle diameter.  The pavilion height of the diamond is measured from the girdle to the culet.  For example, if the pavilion height is 2.69mm and the girdle diameter is 6.25mm, the calculation would be 2.69/6.25=0.43 = 43%, perfect for an ideal cut.

Girdle Thickness: This is the thickness of the girdle.  Girdles are not graded, but rather it is described by its appearance at its thinnest and thickest points.  The descriptions are, extremely thin, thin, medium, slightly thick, thick and extremely thick.  The shape of the diamond will determine which thickness is ideal.   For example, a round brilliant diamond would look best with a thin to slightly thick girdle.  A fancy cut diamond however would do best with a thin to thick girdle to protect it.

Depth: This is the overall depth of the diamond from the table to the pavilion. 

Crown angle: This is the angle that the crown facets intersects the girdle.  This slope is what helps to create the fire in a diamond.  White light entering at the different angles is refracted into its different wave lengths creating the beautiful colors seen in a diamond.

Table percentage: This is the percentage of the table diameter as compared to the entire diamond.  For example, an ideal table percentage for a round brilliant would be 55%.  This means that the table size is 55% the width of the girdle diameter.  For non-round diamonds, this measurement is done by dividing the table length at the wide point with the widest point of the girdle.

Symmetry: This refers to the exactness of the shape and arrangement of facets.  This can include small variations in the alignment of facets or centering of the culet to the diamond as shown in the illustration.  Symmetry is regarded as an indicator of the quality of a diamond's cut and is graded as Poor, Fair, Good, Very Good, Excellent and Ideal.

Just like fingerprints, inclusions and their relative location within the diamond are unique to each diamond.  Diamonds without inclusions are VERY rare and should only be bought from reputable jewelers.  This also makes it nearly impossible for a jeweler to identify flawless diamonds with the same weight and size.  For this reason, some dishonest jewelers will try to sell you a lab created or synthetic diamond and pass it off as a real diamond at a significantly higher price than what it's worth. 

Carbon Spots: Carbon spots are black spots that can be seen within the diamond. 

Feathers: These are small cracks within the diamond.  Small feathers that are well within the interior of the diamond pose little threat to the integrity of the diamond.  However, large feathers or feather near the surface of the diamond should be evaluated extensively as this may affect the integrity of the diamond. 

Knots: This is an inclusion that has reached the surface of the diamond.  Some can be spotted as a raised mark on the polished finish of a diamond

Chips: This is a mark or flaw on the surface of the diamond caused by the breaking of or gouging out of a small piece.  Chips can be caused by a slight impact while wearing or by the setters.  Sometimes people request that their diamond be set low on the mounting reducing the gap between the culet and the base of the head.  That gap acts like a buffer during setting and incase of impacting the finished jewelry by accident.

Needles: This is a long diamond crystal that has formed inside the main diamond.  It looks like a long thin rod within the diamond.

Pinpoints: This is a tiny diamond crystal that has been trapped inside the diamond. 

Clouds: This is a group of pinpoints inside the diamond which appear like clouds.

Fissures: Fissures are feathers or cracks that reach the surface of the diamond.

Fluorescence: Although fluorescence is not a type of inclusion, it can be noticed while looking for inclusions.  This is an effect of some gem-quality diamonds that glow when they are exposed to an ultraviolet light source such as a black light used in special effects.  Most diamonds with fluorescence  will glow blue, but some could glow yellow or white depending on the trace elements in the diamond.  Under normal lighting conditions, fluorescence is not detectable to the naked eye.  Fluorescence can be favorable in certain circumstances.  For example, if a diamond has a yellowish color, a bluish fluorescence can mask the color and make it appear white.  However, diamonds with strong fluorescence can exhibit an oily, milky or cloudy appearance similar to a cloudy inclusion.