Diamonds are widely known for their colorless, brilliant appearance. However, the true spectrum of natural diamonds extends far beyond this traditional notion, encompassing a vast array of colors. These naturally occurring variations are incredibly rare, with only a tiny fraction of all mined diamonds exhibiting a noticeable hue.
The Standard Grading Scale: Near-Colorless Diamonds
The diamond industry uses a standardized D-to-Z color grading scale to evaluate diamonds that are considered near-colorless. This system ranks stones based on the absence of color, with D representing a completely colorless diamond and Z signifying a light yellow or brown tint. Most diamonds encountered in jewelry stores fall within this range, often referred to simply as “white” diamonds.
The slight yellow hue found in the lower end of this scale (K through Z) is typically caused by trace amounts of single nitrogen atoms scattered throughout the crystal lattice. These atoms absorb blue light, allowing a faint yellow color to be transmitted. As the amount of this nitrogen impurity increases, the yellow tint becomes more pronounced.
The Spectrum of Natural Fancy Colors
Diamonds that exhibit a color beyond the Z grade are classified as “Fancy Color Diamonds,” where the presence of color is highly desirable. These stones are exceptionally rare, with fewer than 0.01% of all natural diamonds possessing the necessary color saturation. Unlike the D-Z scale, the value of a Fancy Color Diamond generally increases with the strength and purity of its color.
The major color families include:
- Yellow
- Orange
- Pink
- Red
- Blue
- Green
- Brown
- Black
Yellow is the most common fancy color, often displaying a vibrant canary hue. Brown diamonds, sometimes marketed as Champagne or Cognac, are also relatively abundant.
Blue and Green diamonds are highly sought after, with color intensities ranging from light pastels to deep, vivid shades. Red diamonds are the rarest, with only a handful of true, pure red stones known to exist globally. Pink diamonds, which range from faint rose to intense magenta, are also among the most popular and valuable fancy colors.
How Impurities and Defects Create Color
The vibrant colors found in Fancy Color Diamonds are caused by specific atomic-level impurities or structural defects within the carbon lattice. These mechanisms are distinct from the faint yellowing seen in the D-Z scale. A tiny concentration of foreign atoms or a distortion in the crystal structure is enough to selectively absorb certain wavelengths of light, resulting in a visible color.
The vivid yellow and orange diamonds are primarily colored by nitrogen aggregates, where multiple nitrogen atoms group together within the lattice. This aggregation creates defects that absorb light in the blue-violet part of the spectrum, leaving the complementary yellow or orange light to be transmitted. This mechanism produces a much stronger, more saturated color than the faint yellow caused by single, isolated nitrogen atoms.
Natural blue diamonds, such as the famous Hope Diamond, owe their color to the presence of the trace element boron. Boron atoms substituting for carbon atoms introduce an electron hole into the crystal structure, which causes the diamond to absorb red and yellow light, allowing the blue hue to become visible. This is a particularly rare substitution, making blue diamonds highly valued.
Pink, red, and purple colors do not typically result from chemical impurities but rather from a phenomenon called plastic deformation. Intense stress during the diamond’s journey to the Earth’s surface physically shifts the crystal lattice planes, creating structural defects. These defects selectively absorb visible light, producing the characteristic colors, with the deepest red indicating the most significant lattice distortion.
The natural green color in diamonds is most often caused by exposure to natural radiation during geological time. This radiation knocks carbon atoms out of their positions, creating vacancies that absorb light and appear green. Because the radiation source is often external, the green color in natural stones is frequently concentrated only on the surface of the diamond.