Moonstone Buying and the Four Cs
The IGS moonstone value listing has price guidelines for white cat’s eye, white adularescent, and other color moonstones.
Moonstone color can be separated into body color and adularescence (sheen) color. Ideally, moonstones exhibit a transparent, colorless body with pure blue, medium-toned sheen.
Feldspars can occur in many colors, and moonstones are no different. However, any body color detracts from a moonstone’s value, and unattractive green hues will significantly lower the gem’s price. Peach-pink body colors are popular but not as highly regarded as colorless stones. Brown, yellow, and blue hues also occur.
The adularescent effect itself can also occur in many colors. White is another popular sheen, though not as valuable as blue.
What are Rainbow Moonstones?
Some feldspar gems can display a colorful effect similar to adularescence. Some plagioclase feldspars, like labradorite, can display labradorescence. Although popularly known as “rainbow moonstones,” these gems have a multi-hued sheen that flashes on the surface of the gem. In contrast, adularescence, the distinctive moonstone effect, comes from within the stone. Moonstones are also orthoclase feldspars, not plagioclase.