Understanding Opal: Body Tone, Play-of-Color & Pattern

Opal is unlike any other gemstone. Rather than deriving its beauty from a single bodycolor and clean facets, opal is prized for an optical phenomenon called play-of-color — the shifting flashes of spectral color that move across the stone as it's tilted in the light.

Body Tone

An opal's body tone is its background color, ranging from black and dark grey through to white and colorless "crystal" material. Darker body tones tend to make play-of-color appear more saturated and dramatic, which is part of why black opal commands a premium — but a well-patterned crystal or white opal can be just as captivating in its own way, and much of Ethiopian Wollo material falls into these lighter body tones.

Play-of-Color

Play-of-color happens because opal is made of microscopic silica spheres stacked in a grid. When the spacing between spheres is regular enough, light diffracts as it passes through, splitting into the colors of the spectrum. The strength of this effect is usually described on a scale from faint to vivid, and the range of colors present (dominant flash colors) is often called out specifically — a stone flashing red, green, and blue reads as more valuable than one showing only green.

Pattern

Pattern refers to how the color patches are arranged across the stone's surface. Broad-flash opals show large, sweeping bands of color; pinfire opals show tiny, densely packed points; harlequin and mosaic patterns show a checkerboard-like arrangement of color patches and are amongst the rarest and most sought-after. Floral and honeycomb patterns fall between these extremes.

When you're comparing opals, look at all three characteristics together rather than any single one — a lighter body tone with a vivid, well-patterned flash can be just as compelling as a darker stone with a fainter one.