Anatomy

Diamond Anatomy

The earliest diamond-cutting industry is believed to have started in Venice, Rome a widely recognised trade capital.
The earliest form of diamond cutting is the point cut, with eight symmetrical facets in the shape of an octahedron.
This cut was later improved to a Table Cut, achieved by cutting off part of the top half at the Point Cut to create a table.

Diamond Anatomy

Diamond Anatomy Description

Crown :

Crown, the top part, from the girdle to the table.
It is the top part of the diamond that sits above the girdle.
The crown is composed of bezel facets (crown mains), star facets, upper girdle facets (upper halves), and a table facet.
Crown height may be expressed in mm, or as a percentage of the diamond's average diameter.
Light enters a diamond through the crown facets.

Table :

The uppermost, flat surface of a diamond which runs parallel to the plane of the girdle.
The table is the large flat facet on the crown or top of a diamond.
It directly affects scintillation, or sparkle in a diamond.
The combination of table size and crown angle governs the balance between brilliance, flashes of white light returning to the eye from within the diamond, and dispersion, the play of spectral colors seen by the eye created by refracted light as it prisms through a diamond's facets.

Star Facets :

The facets that sit adjacent to the table called Star Facets.
That is responsible for directing light that enters the diamond down to the pavilion and lower girdle facets.
These triangular facets extend from the table to the upper girdle facets.
There are 8 star facets.

Bezel Facets :

The kite shaped facets that sit between the table and girdle called Bezel Facets.
Also known as the ‘Crown Mains’.
That is responsible for directing light that enters the diamond down to the pavilion and lower girdle facet.
The bezel facets are diamond shaped and sit between the table and the girdle edge.
There are 8 bezel facets on a round brilliant.

Upper Girdle Facets :

The lowest facets on the crown, sitting just above the girdle called Upper Girdle Facets.
Also known as the ‘Upper Halves’.
That is responsible for directing light that enters the diamond down to the pavilion and lower girdle facets.
These triangular facets are closest to the girdle edge.
There are 16 upper girdle facets.

Girdle :

The girdle is the outer edge of a diamond.
The grade of diamonds girdle is determined by the appearance of the girdle at its thinnest point and thickest point.
A diamond's girdle can be faceted, polished smooth, or have a slightly granular appearance.
Very fine cut diamonds often have faceted girdles.
A diamond cutter must spend extra time to carefully facet a girdle’s edge.

Pavilion :

The entire portion of the diamond that sits below the girdle.
A Section from the girdle to the culet.
The lower girdle facets, pavilion facets, and culet are all part of the pavilion.
The pavilion usually constitutes the bulk of a diamond's carat weight and consists of the pavilion facets and culet.
Pavilion height may be expressed in millimeters, or as a percentage of a diamond's diameter.

Lower Girdle Facets :

The highest facets on the pavilion, sitting just below the girdle. These triangular facets extend from the bottom of the girdle to the culet.
Responsible for redirecting light that enters the diamond back out through the crown.
There are 16 lower girdle facets.

Pavilion Facets :

Kite or diamond shaped facets that often take on the appearance of arrows.
There are 8 pavilion mains.
The facets that sit adjacent to the culet, responsible for redirecting light that enters the diamond back out through the crown.

Culet :

A diamond's culet is the point on the bottom of a diamond's pavilion.
The bottom usually comes to a sharp point where the pavilion mains meet.
The culet is the small area at the bottom of the pavilion.
The culet can be a point, or a very small facet sitting parallel to the table.
The facet is measured in terms of size and can be small, medium or large.
Ideally a pointed (none) culet is preferable as a stone with a large culet can be noticed when viewed through the table.

Length :

When viewed from above as a diamond would sit in a ring, length is the diameter measured from ‘Top’ to ‘Bottom’.
Length is expressed in millimeters.
Length is always the first of the three numbers shown under ‘Measurements’ for each diamond.
It is a total width of Crown.
In fancy shape diamonds, length is always longer than width, except in heart shapes, which may actually be wider than they are tall when mounted in a ring.

Width :

When viewed from above as a diamond would sit in a ring, width is the diameter measured from ‘Right Side’ to ‘Left Side’ or vice versa.
Width is always the measure perpendicular to length.
Width is expressed in millimeters.
Width is always the second of the three numbers shown under ‘Measurements’ for each diamond.

Length/Width Ratio :

Calculated by diving the length by the width.
A perfectly round or square shaped diamond has an L/W ratio of 1.00 (since its length and width are equal).
A diamond with an L/W ratio of 1.05 or less will appear perfectly round or square to the naked eye.
It is more commonly used in fancy shapes.
There is no particular L/W ratio in a fancy shape diamond.
What is important is what looks pleasing to you.

Girdle width :

The girdle separates a diamond’s crown and pavilion.
The girdle is described according to its width.
It is measured in terms of thickness.
Ideal girdle thickness should range between Very Thin to Thick.
Sometimes a diamond can have a perfect medium girdle around ninety-nine percent of its diameters.
Diamonds that have grades extremely thin, very thick, or extremely thick are usually not recommended.
If the girdle valleys vary in width, two values are given, one for the widest and one for the narrowest points.

Culet Size :

Any culet size of Medium or smaller will be invisible to the naked eye, and have no negative impact on a diamond's appearance.
To check the culet size, look through the table with your 10x loupe.
With a Very Small culet, tilting the stone might be necessary to make sure there is a culet at all.
A Medium culet will be easy to spot, and you'll probably be able to see the octagon shape.
Slightly Large will be almost visible to the naked eye and you'll easily distinguish the octagon shape under 10x.
A Large to Extremely Large culet will be visible to the naked eye.

Depth :

The 'Depth' of a diamond is the measurement from the table to the culet.
The distance from the table to the culet, the diamond is viewed from the side.
Depth is expressed in millimeters.
Depth is always the third of the three numbers shown under ‘Measurements’ for each diamond.

Depth % :

The depth percentage (%) of a diamond is calculated by dividing the depth by the width of the diamond.
If a diamond is 3mm in depth, and has a width of 4mm, the depth percentage (%) is ‘75’.
The Depth percentage (%) is a measure of cut.
The more shallow the cut of a diamond, the higher the depth percentage (%).
The lower the depth percentage (%), the larger a diamond of a given carat weight, It will appear when viewed from above.

Table % :

The table percentage (%) is calculated by dividing the width of the table by the width of the diamond.
If the table facet is 3mm across, and the diamond is 4mm in width, the table percentage (%) is 75.
The edge of the table is at the mid-point of the star, not the meeting point.
Compare the two lines.
The easiest and the most obvious ratio would be 1:1, for which the divided imaginary line shows equal distances.

Crown Angle :

The crown angle is the angle made between the girdle and the table.
The original ideal angle for the crown is 34.5 °.
This angle was designed to provide the final escape route for the reflected internal light so that the dispersion and brilliance could be viewed.

Pavilion Angle :

The pavilion angle is the angle made between the girdle and the culet.
The original ideal pavilion angle is 40.75 °.
Slight variations from this angle will still produce a well-cut diamond.
This chosen angle accommodates light traveling through the table, reflecting off the inside of the pavilion facets, bouncing to its opposite pavilion facets and leaking through the crown facets surrounding the table.