Color

The GIA Pearl Description System was designed to create an objective, universal way to describe pearl colors. Generally defined, color has three components. Hue is the basic impression of color, for example, blue, green, or yellow. Tone is the color’s lightness or darkness, and saturation is the color’s strength or intensity.

Pearls come in a wide range of hues. Tones cover the whole range from very light to very dark. Saturation doesn’t usually attain the richness that it does, say, in some flowers or paint colors, but it’s still a factor in pearl color descriptions.

Pearl color can have three characteristics:

Bodycolor—The dominant, overall color of the pearl.

Overtone—A translucent color that appears over a large area of a pearl’s surface.

Orient—More than one translucent color over the bodycolor, or surface iridescence.

All pearls display bodycolor. It’s mainly caused by natural pigments embedded in the conchiolin. The pigments vary with mollusk species and with individuals within each species. Other factors that can help determine a pearl’s bodycolor include the color of the mantle-tissue implant that’s used for pearl culturing, substances in the water, and the nature of the mollusk’s food.

Some pearls display overtone, a translucent color that appears over the bodycolor. Overtone is always secondary to bodycolor. When present, it’s usually visible over the entire pearl or a large part of it. The most common overtone colors are green, blue, and pink.

 

Fewer pearls display orient than overtone, although both effects are caused by the same complex interaction of nacre and light. Orient occurs over a much smaller area than overtone and most often on nonspherical pearls with irregular surfaces. Orient is surface iridescence that can consist of several colors of the rainbow.