The Anatomy Of A Diamond: Introduction To Diamond Terminology And Shared Elements Between Diamonds

 

A polished diamond consists of many different elements contributing to the overall appearance of the stone. Even though each diamond is unique, many diamonds do have common structural elements. The relationship between each element influences the characteristics of the diamond such as proportion, reflection, dispersion and refraction. This article will specifically look into the round brilliant cut unless mentioned otherwise.

 

What Are The Main Sections Of A Diamond?

The first step to understanding the anatomy of a diamond is to get familiar with four main parts that determine the shape most diamonds: the crown, the girdle, the pavilion and the facets.

 

Crown

The crown refers to the upper portion of a diamond that ranges from the table to the girdle. In some cases, the crown can be raised but sometimes crowns may be cut very high, flat, or even concave.

ROUND_DIAMOND_CROWN_SIDE_VIEW

Girdle

The girdle denotes the belt between the top part of the diamond, known as the crown, and the bottom part known as the pavilion.

ROUND_DIAMOND_GIRDLE_SIDE_VIEW

Pavilion

The pavilion refers to the bottom part of the diamond that ranges from the girdle to the culet. The pavilion usually has a recognizable V-shape and is often ‘hidden’ under the ring setting.

ROUND_DIAMOND_PAVILION_SIDE_VIEW

Facet

A facet refers to a flat area arranged in a geometrical shape on the diamond’s surface. Facets improve the appearance of a diamond by allowing the stone to reflect light in particular directions. Diamond usually have various types of facets cut into them to achieve the most appealing look.

 

 

What Are The Main Elements Of A Crown?

As noted above, the crown refers to the upper portion of a diamond and consist of multiple elements. The most important elements of the crown are: the table facet, star facets, bezel facets and upper half facets.

 

Table Facet

The table is the widest or largest facet of a diamond and is located at the top of the stone. When light enters the diamond, the table refracts the light and sends it in all directions to the other facets. This causes the diamond to sparkle and glimmer.

ROUND_DIAMOND_TABLE_FACET_TOP_VIEW

Star Facet

Star facets are the triangular facets alongside the edge of the table. For example with round brilliants, the diamonds usually have a ring of eight star facets adjoining the table.

ROUND_DIAMOND_STAR_FACET_TOP_VIEW

Bezel Facet

Bezel facets, sometimes referred to as kite facets because of their shape, are larger facets that sit between the table and the girdle.

ROUND_DIAMOND_BEZEL_FACET_TOP_VIEW

Upper Half Facet

Upper half facets, also known as upper girdle facets, are the facets that border the girdle from the top of the diamond.

ROUND_DIAMOND_UPPER_HALF_FACET

 

What Are The Main Elements Of A Girdle?

The girdle is the belt connecting the crown and the pavilion. The most important elements of the girdle are the girdle facets.

 

Girdle Facets

Girdle facets are the small facets covering the entire belt. Faceted girdles are blended in with the crown and the pavilion. However, not every girdle is faceted.

 

 

What Are The Main Elements Of A Pavilion?

The pavilion is the lower part of a diamond that often has a V-shaped appearance. The most important elements of the pavilion include: the lower half facets, the pavilions facets and the culet.

 

Lower Half Facet

The lower half facets, also known as lower girdle facets, border the girdle from the bottom of the diamond.

ROUND_DIAMOND_LOWER_HALF_FACET_SIDE_VIEW

Pavilion Facet

The pavilion facets, sometimes referred to as pavilion main facets, stretch from the culet towards the girdle.

ROUND_DIAMOND_PAVILION_FACET_SIDE_VIEW

Culet

The culet refers the very bottom tip or smallest point of the stone. The pavilion of many diamonds is cut with a culet facet. However, not all gemstones are cut with a culet facet. When a diamond does not have a culet facet, it is also known as a “pointed culet”.

 

 

Other Terms And Ratios Used To Describe The Anatomy Of A Diamond

Besides the facets elements making up the crown, girdle and pavilion, other elements and ratios are just as important to the overall quality and appearance of the diamond.

 

Break Facet

Break facets refers to the facets bordering the girdle from both the crown and the pavilion. The facets bordering the girdle from the side of the crown are call upper half facets, whereas the facets bordering the girdle from the pavilion are referred to as lower half facets.

 

Crown Facet

The term crown facets refers to all the facets that are located on the crown, such as star facets, bezel facets and upper half facets

 

Depth

The depth of a diamond refers to the height of a diamond that is measured from the table to the culet.

 

Diameter

The diameter of a stone refers to the distance from  girdle edge to girdle edge. This line crosses the center of the stone.

 

Keel

Many diamond are cut to form more of an edge rather than a culet or pointed culet. This is the edge where the facets of the pavilion meet. This area is known as ‘keel’ or ‘keel-line’ as it resembles the bottom of a ship.

 

Mains

The largest facets of a diamond are known as mains. Mains are located on both the crown and the pavilion.

 

Meet

Meet refers to the junction of two facets.

 

Meet Point

Meet point refers to the junction of three or more facets.

 

Depth Percentage

The depth percentage refers to the proportion between the depth (i.e. height) of a diamond and its average girlde diameter. This percentage influences the brilliance of the stone. When a diamond’s depth percentage is too low, the stone will look dark or shallow because the light is not reflected well enough. When a diamond’s depth percentage is too high, the diamond will look dull because too little light is visible from the top of the diamond. The formula for calculating the depth percentage is:

Depth Percentage = (Diamond Depth / Average Girdle Diameter) x 100

ROUND_DIAMOND_DEPTH_PERCENTAGE

Length-To-Width Ratio

The length-to-width ratio describes the proportions of a diamond. Each diamond shape has its own range of suitable length-to-width ratio. This means that the ideal length-to-width ratio depends mainly on the shape of the diamond. Round shapes should fall close to 1, whereas rectangular and oval shapes should be longer than they are wide and their ratio typically ranges from 1.25 – 2. The length-to-width ratio can be calculated via this formula:

Length-To-Width Ratio = Diamond Length / Diamond Width

ROUND_DIAMOND_LENGTH_TO_WIDTH_RATIO

Crown Angle

The crown angle refers to the angle between the table plane and the bezel facet plane. Generally, the average of eight measurements is taken and uses the nearest half of a degree (i.e. 0.5°) for final reporting. The crown angle can influence the brightness and attractiveness of a diamond.

ROUND_DIAMOND_CROWN_ANGLE

Crown Height Percentage

The crown height is measured from table to the intersection between the bezel facet and the girdle. This measurement is divided by the average girdle diameter. The formula for calculating the crown height percentage is:

Crown Height Percentage = (Crown Height / Average Girdle Diameter) x 100

ROUND_DIAMOND_CROWN_HEIGHT_PERCENTAGE

Table Percentage

The table percentage refers to the relationship between the table size and girdle diameter. The ideal table percentage depends on the type of diamond shape. When the table percentage is too low or too high, light will not be refracted well which makes the stone less sparkling and appealing. The table percentage is calculated via the following formula:

Table Percentage = (Average Table Size / Average Girdle Diameter) x 100

ROUND_DIAMOND_TABLE_PERCENTAGE

Star Length Percentage

The star length percentage represents the length of the star facets in relation to the girdle-to-table distance. The star length percentage is calculated using the following formula:

Star Length Percentage = (Star Facet Length / Girdle-To-Table Distance) x 100

ROUND_DIAMOND_STAR_FACET_LENGTH_PERCENTAGE

Girdle Thickness

Girdle thickness described how wide the girdle is. The girdle is usually classified between ‘Extremely thin’ to ‘Extremely tick’. When a girdle is too thin it makes the diamond more vulnerable. When a diamond has a thin girdle it is easier for the stone to chip or become deformed by prongs used to hold the diamond in its place. On the other hand, girdles that are too thick influence the look and feel of the stone. When a diamond has a thick girdle, it doesn’t reflect light optimally and makes the stone appear too small for its carat size.

 

Pavilion Angle

The pavilion angle refers to the angle between the table plane and the main pavilion’s main facet planes.

ROUND_DIAMOND_PAVILION_ANGLE

Pavilion Depth Percentage

The pavilion depth is measured from the culet to the intersection of the pavilion facets and the girdle. The average of the pavilion depth is divided by the average girdle diameter. The formula for calculating the pavilion depth percentage is:

Pavilion Depth Percentage = (Average Pavilion Depth / Average Girdle Diameter) x 100

ROUND_DIAMOND_PAVILION_DEPTH_PERCENTAGE

Culet Width

Culet width refers to the size of the culet. Culet width ranges from none to extremely large.

ROUND_DIAMOND_CULET_WIDTH



Summary

A diamond consists of various elements that make each stone unique. However, even though each stone is unique, the anatomy of most diamonds has one or more common elements. Some of these well-known elements include:

 

Diamond Sections

  • Crown, the upper portion of the diamond.
  • Girdle, the belt in between the crown and the pavilion.
  • Pavilion, the lower portion of the diamond.

Crown

  • Table facet, the largest facet on top of the stone.
  • Star facets, small facets adjoining the table.
  • Bezel facets, larger facet shaped like a kite.
  • Upper half facets, facets adjoining the girdle from the top of the diamond.

Girdle

  • Girdle facets, small facets on the girdle.

Pavilion

  • Lower half facets, facets adjoining the girdle from the bottom of the diamond.
  • Pavilion facets, large facets extending from the culet towards the girdle.
  • Culet or Keel, lowest tip or point of a diamond.

Other Diamond Terms, Angles And Ratios

  • Break facets, facets bordering the girdle from the top and bottom of the diamond.
  • Depth, height of the diamond.
  • Keel, the edge at the bottom of the diamond.
  • Meet, junction of two facets.
  • Meet point, junction of three or more facets.
  • Depth percentage, the proportion of diamond depth and average girdle diameter.
  • Length-to-width ratio, describes the proportions of the diamond.
  • Crown angle, angle between the table plane and the bezel facet plane.
  • Crown height percentage, the proportion of crown height to average girdle diameter.
  • Table percentage, the proportion between average table size and average girdle diameter.
  • Star length percentage, the proportion between star facet length and girdle-to-table distance.
  • Girdle thickness, the width of the girdle.
  • Pavilion angle, the angle between the table plane and the pavilion facet plane.
  • Pavilion depth percentage, ratio between average pavilion depth and average girdle diameter.
  • Culet width, the size of the culet.

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