Diamond Cuts and Shapes

Diamond Anatomy

Diagram of diamond anatomy

These illustrations show the four greater parts and the lesser parts that make up the facets of a round brilliant diamon.

Polished diamond has 4 great parts: the table, the crown, the girdle, and the pavilion.

A round brilliant diamond has between 57 and 58 facets (depending on whether the culet was polished into a facet or closed to a point):

  • Table: 1 facet.
  • For the crown: 8 bezels, 8 stars, and 16 upper girdle facets.
  • For the pavilion: 8 pavilions and 16 lower girdle facets.
  • Culet: 1 or 0 facet (if no culet facet). Also, in higher quality goods the girdle is frequently faceted, but these facets are not counted in the total.

Cut and Shape

Round Billiant

The Most Popular Cut

Round Brilliant Diamond

Oval Diamond

Marque Diamond

Radiant Diamond

Cushion Diamond

Emerald Cut Diamond

Pear Cut Diamond

Princess

Asscher Diamond

Trillion

Heart Shaped Diamond

Bauggete

Proportions

Proportionscope:

  • The tool used to measure the proportions of a diamond
  • It is necessary to consider all the proportions and not only some of them. An angle of crown too large or too small is indicated in remark.
  • An open culet indicates a poor stone (except in the case of the old cuts).
  • In melee, thick rondists indicate not very interesting stones.
  • Many professionals consider the cut the most important diamond characteristic because even if a diamond has perfect colour and clarity, a diamond with a poor cut will have dulled brilliance.
  • For those how wish more information regarding the proportions of the brilliant cut, they will know that in 1919, Marcel Tolkowsky published « Diamond Design » in which he describes his research on the proportions of the brilliant cut.

The Ideal Cut

It is a very vast subject, which divides the professionals still today. To obtain the maximum of brightness, fire, « life », a diamond must be cut according to certain dimensions and proportions. The diamond cutters must carefully consider the optical properties of each diamond to determine its optimal size.

The brilliance of a diamond is produced by the proportions of its cut.

Ideal Cut

Light is correctly reflected. Diamond has a beautiful brilliance and fire.

Too Shallow

Light is lost out the sides causing the diamond to lose brilliance

Too Deep

Light escapes out the bottom causing the diamond to appear dark and dull

To obtain an ideal cut, the 3 principal elements, are total depth, table size, and girdle thickness

Total Depth Percentage (%)

To obtain an ideal cut, the 3 principal elements, are total depth, table size, and girdle thickness. Other factors must also be considered, as well.

Table Percentage (%)

TableOnly round diamonds have a standard for table size. In round diamonds for a diamond to be recognized as an ideal cut the table must be relatively small. It must fall between 53% and 57%

Girdle Thickness

The best girdle range for a diamond to fit in the ideal cut category for rounds is anywhere between « Thin » and « Slightly Thick ». The girdle could be Thin, Medium, Slightly thick or any combination of the three, such as « medium to slightly thick ». The various graduations thickness of the rondist are: Extremely thin, Very thin, Thin, Medium, Slightly thick, Thick, Very thick and Extremely thick.

Cutlet Size

Other elements are important, such as the culet size. The culet size is listed on a certificate and your diamond’s culet should be pointed (no culet), very small, small or medium because these are not visible to the naked eye. The graduations of the culet size are: No Culet, Pointed, Very Small, Small, Medium, Large, Very large and Extremely large. Avoid the culets equal or lower than « Large » which when you look at diamond by the table are very visible with the naked eye.

Girdle Polish

The girdle of diamond can be faceted, polished or rough. Diamonds which has a very beautiful cut have often the faceted girdle. A diamond cutter must work from additional time to facet it, which is not always economically profitable. A faceted girdle does not improve quality of diamond. The GIA evaluates only the thickness of the girdle and not its appearance.

Finish

Symmetry

  • The estimate of  “symmetry” results from the observation from:
    • The good alignment of the facets.
    • The symmetry of the facets.
    • The centering of the cutlet.
    • The centering of the table.
  • A diamond can have good symmetry and poor proportions.

Some examples of symmetry defects:

Eccentric Table

Eccentric Cutlet

Deformed Girdle

Deformed Cutlet

Misaligned Crown Pavilion

Undulating Girdle

Polish

The estimate of the polish results from the observation from:

  • The presence of more or less polish lines.
  • The presence of stripes.
  • The number of polish stripes

The estimate of symmetry and polished results in: Excellent, Very good, Good, Fair, Poor.