What Is Diamond Brilliance?

Diamond brilliance is the captivating play of white light reflected from the internal and external surfaces of a diamond. It is one of the key attributes that make diamonds so alluring and valuable. Understanding diamond brilliance involves delving into the science of light reflection and refraction, as well as the craftsmanship behind the diamond cut. At Cathy Eastham Fine Jewelry, we pride ourselves on offering diamonds with exceptional brilliance. This blog will explore the concept of diamond brilliance and the essential factors involved in assessing it.

Understanding Diamond Brilliance

Definition of Brilliance

Diamond brilliance refers to the intense white light that radiates from a diamond when it is exposed to light. This dazzling effect is created by the reflection and refraction of light within the diamond. Brilliance is different from fire (flashes of color) and scintillation (sparkle), but all three contribute to the overall visual appeal of a diamond.

The Role of the Cut

The cut of a diamond is the most crucial factor in determining its brilliance. A well-cut diamond will reflect light internally from one facet to another and then return it to the observer’s eye, creating a radiant glow. The proportions, angles, and finish of the cut play significant roles in this process.

Components of Diamond Brilliance

Light Performance

Light performance is a measure of how well a diamond interacts with light. It involves the diamond’s ability to capture light, reflect it internally, and return it to the observer’s eye. Diamonds with high light performance exhibit excellent brilliance, fire, and scintillation.

Proportions and Angles

The proportions and angles of a diamond’s facets are critical in maximizing light performance. Important factors include:

  • Table Size: The flat surface on the top of the diamond. An optimal table size allows for the right amount of light to enter and reflect within the diamond.
  • Crown Angle: The angle between the girdle and the top of the diamond. Proper crown angles help in dispersing light effectively.
  • Pavilion Depth: The depth from the girdle to the bottom of the diamond. Correct pavilion depth ensures that light is reflected back to the top of the diamond, rather than leaking out from the sides or bottom.

Symmetry and Polish

Symmetry refers to the exactness of the diamond’s shape and the alignment of its facets. A symmetrical diamond will reflect light evenly, enhancing its brilliance. Polish refers to the smoothness of the diamond’s surface. High polish quality reduces surface imperfections that can scatter light, thus maintaining the diamond’s brilliance.

Light Performance in Diamonds

Light performance is a critical aspect of a diamond's overall appeal, encompassing how effectively a diamond captures, reflects, and returns light to the observer's eye. High light performance results in a captivating display of brilliance, fire, and scintillation, making the diamond appear more vibrant and lively. 

Components of Light Performance


Brilliance refers to the white light that is reflected from the diamond's surface and its internal facets. A diamond with high brilliance will appear bright and full of life, reflecting white light back to the viewer's eye in a dazzling manner.

  • External Reflection: The light that reflects off the diamond's surface facets.
  • Internal Reflection: The light that enters the diamond, reflects off the internal facets, and exits through the top of the diamond.


Fire is the dispersion of light into its spectral colors, creating flashes of color within the diamond. This effect is seen as the diamond moves and catches light at different angles.

  • Dispersion: The splitting of white light into its component colors (red, orange, yellow, green, blue, indigo, and violet).
  • Spectral Colors: The colorful flashes that are visible as the diamond interacts with light.


Scintillation refers to the sparkle and pattern of light and dark areas that move across the diamond's surface when it is moved. It is a dynamic play of light that adds to the diamond's overall visual appeal.

  • Sparkle: The small, bright flashes of light seen as the diamond moves.
  • Pattern: The distribution of light and dark areas within the diamond, contributing to its visual texture.

Factors Influencing Light Performance

Cut Quality

The cut quality of a diamond is the most significant factor affecting its light performance. A well-cut diamond will exhibit optimal proportions and symmetry, allowing it to reflect and refract light efficiently.

  • Proportions: The relative measurements of a diamond's facets, including table size, crown height, pavilion depth, and girdle thickness.
  • Symmetry: The precise alignment and arrangement of a diamond's facets. High symmetry ensures that light is evenly distributed and reflected within the diamond.

Proportions and Angles

The proportions and angles of a diamond's facets determine how light travels through the stone. Ideal proportions allow for maximum light reflection and refraction, enhancing the diamond's brilliance, fire, and scintillation.

  • Table Size: The flat top surface of the diamond. An ideal table size allows sufficient light entry and optimal internal reflection.
  • Crown Angle: The angle between the girdle and the top facet of the diamond. Proper crown angles help disperse light and create fire.
  • Pavilion Depth: The depth from the girdle to the bottom facet of the diamond. Correct pavilion depth ensures light is reflected back to the top of the diamond rather than escaping through the sides or bottom.

Polish and Symmetry

Polish and symmetry are crucial for maximizing a diamond's light performance. A well-polished diamond has a smooth surface that reduces light scattering, while high symmetry ensures even light distribution within the diamond.

  • Polish: The quality of the diamond's surface finish. Excellent polish results in fewer surface imperfections that could scatter light.
  • Symmetry: The uniformity and alignment of the diamond's facets. High symmetry enhances the diamond's ability to reflect light effectively.

Assessing Light Performance


Certification from reputable gemological laboratories, such as the Gemological Institute of America (GIA) or the American Gem Society (AGS), provides an objective assessment of a diamond's cut quality, proportions, polish, and symmetry. These factors are critical in determining light performance.

  1. Cut Grade: Ranges from Excellent to Poor. An Excellent cut grade indicates optimal light performance.
  2. Proportions and Angles: Detailed measurements provided in the certification report.
  3. Polish and Symmetry Grades: Separate assessments that contribute to the overall cut grade.

Visual Inspection

Visual inspection allows for a subjective evaluation of a diamond's light performance. Observing the diamond under various lighting conditions and viewing it from different angles can help assess its brilliance, fire, and scintillation.

  1. Lighting Conditions: Different light sources, such as daylight, LED, and incandescent lights, can affect the perception of a diamond's light performance.
  2. Angle Observation: Viewing the diamond from multiple angles to ensure consistent brilliance and fire.
  3. Movement: Moving the diamond to observe its scintillation and sparkle.

Enhancing Light Performance Through Settings

The setting of a diamond can significantly influence its light performance by maximizing light exposure and reflection.

  • Prong Settings: Allow maximum light exposure by minimizing metal obstruction. Ideal for enhancing brilliance and scintillation.
  • Bezel Settings: Surround the diamond with a thin metal rim, protecting the stone while allowing light to enter from the top. Reflects light back into the diamond, enhancing its fire.
  • Halo Settings: Surround the central diamond with smaller diamonds, reflecting light into the center stone and amplifying its brilliance.


Diamond brilliance is a multifaceted attribute resulting from precise cutting, optimal proportions, and expert craftsmanship. Each aspect, from the angles and symmetry to the polish and proportions, plays a crucial role in maximizing a diamond's ability to capture and reflect light, creating that enchanting sparkle.

At Cathy Eastham Fine Jewelry, we are committed to offering diamonds that exhibit exceptional brilliance, ensuring that each piece of jewelry is a testament to elegance and beauty. Visit our store at 2101 W Wadley Suite 31, Midland, Texas 79705, or contact us at Cathy@cathyeastham.com or (432) 682-8008 by call or text. Our hours are Monday to Friday, 10am – 5:30pm, and Saturday by appointment.

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