Polished Diamond Guide Diamond Cut and Diamond Shape Guide

Diamond Cut and Diamond Shape Buying Guide

Diamond Anatomy
Shape and Cut
Proportions
Finish

Diamond Anatomy

Diamond has 4 great parts:

Table
Crown
Girdle
Pavilion

A Round Brilliant Cut 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.

Pictures of the Most Popular Diamond Shapes

Round Brilliant Diamond

Videos of the Most Popular Diamond Shapes:

Other Shapes

History of the various shapes

The number of diamond facets

Calculating brilliant cut diamond: diameter/weight

Gallery of images of various shapes and cuts: 77 listed shapes

Proportions

The tool used to measure the proportions of a diamond is a proportionscope.

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 color 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. You can click on this link and search his work: Tolkowsky

The « ideal » Diamond 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.

Brilliance of a diamond following the proportions of its cut:

Ideal Cut: light is correctly reflected. Diamond has a beautiful brilliance.

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:

1) Total Depth %:

The height of the stone is divided by the diameter in rounds or by the width in all other shapes. Say the stone measures 6.52 - 6.56mm x 3.92mm, the total depth is 3.92mm ÷ 6.54mm = 59.93%. Ideal round diamonds should have a depth of 59%-62.50%.

2) Table Percentage (%):

Only 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%.

3) 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.

	Girdle Thickness
	Extremely thin	Very thin	Thin	Medium	Slightly thick	Thick	Very thick	Extremely thick
Extremely thin	GD	VG	VG	VG	VG	VG	GD	FR
Very thin		VG	VG	VG	VG	VG	GD	FR
Thin			EX	EX	EX	VG	GD	FR
Medium				EX	EX	VG	GD	FR
Slightly thick					EX	VG	GD	FR
Thick						VG	GD	FR
Very thick							GD	FR
Extremely thick								FR

FR = Fair --- GD = Good --- VG = Very Good --- EX = Excellent

4) Others :

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.

GIA Culet Size:

Culet Size	Grade
None	Excellent
Very small
Small
Medium	Very Good
Slightly large	Good
Large	Good
Very large	Fair
Extremely large	Poor

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.