Advanced Diamond Quality Guide: Polish, Symmetry, Table & Fluorescence

Beyond the well-known 4 C’s of diamonds — Cut, Colour, Clarity and Carat Weight —
several additional grading factors influence a diamond’s overall beauty and brilliance. Professional gemologists also examine elements such as polish, symmetry, table percentage, and fluorescence when assessing diamond quality.

Understanding these advanced characteristics provides deeper insight into a diamond’s craftsmanship and light performance. At Cerrone, our diamond experts carefully evaluate every detail to ensure each stone meets the highest standards of brilliance and refinement.

POLISH

Diamond polish refers to the smoothness and quality of a diamond’s facet surfaces after the cutting and finishing process.

During the final stage of diamond cutting, the diamond is polished to remove microscopic marks left by the cutting wheel. When a diamond is perfectly polished, its facets appear smooth and mirror-like, allowing light to reflect cleanly throughout the stone.

If the polish is poor, tiny polishing lines or burn marks can interfere with the way light travels through the diamond, slightly reducing brilliance.

Diamond polish is typically graded as:


  • Excellent

  • Very Good

  • Good

  • Fair

  • Poor

High-quality diamonds usually feature Excellent or Very Good polish, ensuring optimal light reflection and a beautifully finished surface.

At Cerrone, diamonds are selected with exceptional polish to enhance brilliance and overall visual refinement.

SYMMETRY

Diamond symmetry evaluates the precision with which a diamond’s facets align and interact with one another.

A well-cut diamond contains dozens of facets arranged in exact proportions. If these facets are perfectly aligned, light is reflected evenly throughout the diamond, creating superior brilliance and sparkle.

Poor symmetry can cause light leakage or uneven reflections, diminishing the diamond’s visual performance.

Diamond symmetry is graded on a similar scale:


  • Excellent

  • Very Good

  • Good

  • Fair

  • Poor

Diamonds with Excellent symmetry display highly precise facet alignment and exceptional optical balance.

Our diamond specialists carefully select stones with superior symmetry to ensure optimal brilliance.

Fluorescence

Fluorescence refers to a diamond’s reaction to ultraviolet (UV) light. Some diamonds emit a soft glow — usually blue — when exposed to UV light.

Fluorescence is a natural characteristic present in approximately 25–35% of diamonds.

Diamond fluorescence is graded as:


  • None

  • Faint

  • Medium

  • Strong

  • Very Strong

In most lighting conditions, fluorescence is not visible to the naked eye.

In some diamonds, faint or medium fluorescence can actually improve the appearance of slightly warm colour grades by making the diamond appear whiter in daylight.

However, very strong fluorescence may occasionally cause a diamond to appear slightly hazy.

Our experts carefully assess fluorescence to ensure it enhances rather than detracts from a diamond’s beauty.

TABLE

The table is the large flat facet located at the top of a diamond. It is one of the most important elements affecting how light enters and exits the stone.

  • The size of the table is expressed as a percentage of the diamond’s overall width.

Ideal Diamond Table

If the table is too large:


  • Light may escape through the bottom of the diamond

  • Brilliance can appear reduced

If the table is too small:


  • The diamond may appear darker

  • Light dispersion may be limited

For many round brilliant diamonds, an ideal table percentage typically falls between 54% and 60%, although optimal proportions vary slightly depending on the diamond’s shape.

A balanced table proportion allows light to enter the diamond efficiently and reflect back through the crown, maximising brilliance.

DEPTH

Diamond depth refers to the total height of a diamond measured from the table (top surface) to the culet (the bottom point). This measurement is expressed as a percentage of the diamond’s width, known as the depth percentage.

Depth is one of the most important factors influencing how a diamond interacts with light. When the depth of a diamond is properly proportioned, light entering the stone reflects internally and returns through the top of the diamond, creating the brilliance and sparkle that diamonds are celebrated for.

If a diamond is cut too shallow, light escapes through the bottom of the stone rather than reflecting back to the viewer. This can make the diamond appear watery or lacking in brilliance.

If a diamond is cut too deep, light may escape through the sides of the diamond, causing the stone to appear darker and sometimes smaller than its carat weight suggests.

Ideal Diamond Depth Percentage

For many round brilliant diamonds, an ideal depth percentage typically falls between 59% and 62.5%. Within this range, the diamond’s proportions allow optimal light reflection and brilliance.

However, the ideal depth can vary slightly depending on the diamond’s shape, as fancy shapes such as oval, cushion, emerald and radiant cuts require different proportions to maximise their beauty.

Why Diamond Depth Matters

A well-balanced depth ensures:


  • Maximum brilliance and light return

  • Proper visual size relative to carat weight

  • Harmonious proportions throughout the diamond

  • Superior sparkle and fire

At Cerrone, our diamond specialists carefully analyse diamond proportions, including depth percentage, to ensure every diamond displays exceptional brilliance and visual balance.

Why Diamond Craftsmanship Matters

Beauty is not determined by size alone. True brilliance comes from precision cutting, expert polish, perfect symmetry, balanced table, optimal depth, and ideal proportions. Cerrone selects diamonds where every factor is harmoniously aligned, creating a stone of unrivaled radiance.