Diamond Advanced Guide

DIAMOND ADVANCED GUIDE

Beyond the four C's, this advanced guide will help you understand how experts judge a diamond's character.

Polish

A diamond’s polish refers to the condition of the gemstone’s surface and its overall smoothness. Whereas Clarity involves the flaws within the stone, polish is graded by surface flaws only. This is a result of the polishing process undertaken by the cutter, and flaws may be exacerbated over time from handling, wear and tear.

A diamond with an “Excellent/Ideal” polish grade has a very smooth surface, and allows light to enter and exit the stone most efficiently. This will provide the highest level of luster when the diamond shines. Better polish grades are usually achieved by the gemstone cutter polishing the stone for a longer time, and by using better equipment such as a high-grade polishing wheel with finer grade diamond dust. Polish goes hand-in-hand with a diamond’s symmetry in affecting the overall fire and brilliance.

polish-Image

Symmetry

Symmetry refers to the equality of the diamond shape, its overall outline, and the placement, preciseness and alignment of individual facets. An excellent symmetrical cut will allow the light to intersect with the facets properly, and direct the light in the most efficient manner. A diamond with poor symmetry may misdirect light entering the diamond, therefore reducing the level of luster and brilliance from the stone.

The main goal of a gemstone cutter is to make careful decisions that yield the maximum value out of the rough stone. It’s important to know that a diamond cutter may make deliberate flaws within the symmetry of a cut, usually in order to yield a higher carat weight or to omit an unattractive inclusion. Diamonds with a symmetry grade of Good to Excellent will still yield an exceptional appearance if the polish and cut have a high grade. Symmetry is more important in diamonds with a VVS2 Clarity or higher, because poor symmetry would compromise its near flawless clarity.

symmetry
  • excellent

    excellent

  • very-good

    very good

  • good

    good

  • fair

    fair

  • poor

    poor

Depth

One of the most important proportions that contributes to a diamond’s appearance, brilliance and fire is the depth of the stone. The depth is calculated by taking the height of a diamond, measured from the culet to the table, and dividing by its average girdle diameter. It’s important to have balance between the table width and depth of the stone to achieve ideal sparkle and beauty.

  • deep

    top deep

  • ideal

    ideal

  • shallow

    too shallow

Table

The table is usually the largest facet on a diamond, and it’s always located on the very top. The size of the table can have a vital role in the diamond's light performance and brilliance. It’s widely misunderstood that a larger table would make a diamond more brilliant than one with a smaller table. Rather, the depth of the stone, symmetry and other factors will affect the overall quality. The table percentage is calculated based on the size of the table divided by the girdle diameter. The following diagram helps to show some variances in table percentage.

table-img
table-img

Fluorescence

A diamond’ fluorescence is a measure of the visible light emitted when exposed to ultraviolet (UV) rays. About 30% of diamonds have fluorescence to some degree, and it shouldn’t be a major factor in the purchase of a diamond. It is quite rare for fluorescence to have any visual impact on a diamond's appearance, and it does not compromise the gem's structural integrity in any way. Diamonds with a strong or very strong fluorescence aren’t usually noticeable to the naked eye unless the diamond is a D-F color grade. Strongly fluorescent diamonds are also a better value, due to the market pricing them slightly lower.

fluorescence-img
fluorescence

Cut Anatomy

It’s helpful to know the different names of the areas of a diamond. A diamond is composed of five main areas from top to bottom: the table, the crown, the girdle, the pavilion, and the culet.

Hover over the diamond diagram to explore

crown

The circle of facets around the table, working with the table to redirect the light throughout the stone.

table

The flat surface top that shows most prominently when viewing the stone.

girdle

where the diamond gets its main shape, and separates the top and bottom of the stone.

pavilion

The lower area of the diamond, where facets serve to highlight the brilliance of the stone.

culet

Bottom tip of the diamond.

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