Color

Diamond Color Grading System Analysis

Color Grading Standards

The international diamond industry employs the ​GIA D-Z Color Scale, categorizing diamonds from colorless (D) to light yellow/brown (Z). This system divides diamonds into five key groups:

Comparison of color and near colorless diamonds, showing different shades and their color intensity, with round diamond cut examples for each shade.

  • ​D-F (Colorless):​​ Requires 10X magnification for detection, containing <0.5ppm nitrogen

Close-up of a round-cut diamond and a flat diamond on a grey background.
Close-up of a round, faceted diamond reflecting light, with its reflection visible on a smooth surface.

D Color

Close-up of a round-cut diamond showing both top view and side view

E Color

F Color

  • ​G-J (Near Colorless):​​ Detectable only in face-down comparison with masterstones

Close-up of a round brilliant-cut diamond and a loose diamond from a side view.
Close-up of a round brilliant cut diamond with a view of the top and side facets

G Color

Close-up of a round, cut diamond viewed from the top and side angles on a light background.

H Color

Close-up of a round cut diamond gemstone from top and side views.

I Color

  • K-M (Faint Yellow):​​ Noticeable yellow tint visible to untrained eye

J Color

Close-up of a clear round-cut diamond, showing both top view and side view.

K Color

While yellow remains the most prevalent diamond color, brown hues are frequently observed in nature. Current gemological research indicates that this chromatic manifestation primarily arises from ​plastic deformation-induced lattice distortions​ during diamond formation, often interacting with trace nitrogen impurities . The structural irregularities create vacancy clusters or dislocation networks that absorb specific light wavelengths, producing the characteristic brown tones. Notably, nitrogen atoms may act as catalysts rather than direct chromophores in this process

A round, faceted diamond above a side view of the same diamond showing its profile.
Close-up of a round brilliant cut diamond from a side view showing its facets and profile.
A pear-shaped diamond gemstone photographed from both top and side views.
A rectangular-cut clear gemstone, possibly a diamond, placed on a light background, with its reflection visible below.

​N-Z (Light Color):​​ Significant color impact on brilliancecolor impact on brilliance

Color Assessment Protocol

Professional evaluation requires:

  1. ​Standardized Lighting:​​ Illuminant D65 (6500K) with 5500-6500 lux intensity

  2. ​Neutral Background:​​ White or gray comparison surfaces

  3. ​Facet Analysis:​​

    • Table-up observation for crown reflections

    • Pavilion-side examination for light leakage

  4. ​Fluorescence Testing:​​ UV-induced color changes measured on GIA scale (None to Very Strong)

Optical Performance Metrics

ParameterD-F GradeK-M GradeReflectance (%)97.5-98.589.2-92.1Brilliance Index100 (Reference)63-78Fire Intensity3.2-3.8 (×10³ sr)1.9-2.4 (×10³ sr)

Special Color Phenomena

  • ​Brown Tones:​​ Caused by plastic deformation and nitrogen clusters

  • ​Fluorescence Impact:​​ Strong fluorescence (>3) may reduce value by 5-15%

  • ​Color Zoning:​​ Layered color distribution requiring >3mm uniformity for premium grades