“Rainbow moonstone” is one of the most misunderstood names in the gem world. Despite carrying “moonstone” in its name, it isn’t technically moonstone at all, and understanding why changes how you should think about buying and valuing it.
The Name That Confuses Everyone
Traditional moonstone is a variety of orthoclase feldspar, specifically a form called adularia. Rainbow moonstone is a different mineral entirely: transparent labradorite, which belongs to the same broader feldspar family but is chemically distinct.
The Gemological Institute of America addresses this directly. Their position is that rainbow moonstone is technically labradorite, not true moonstone, but because it’s such a closely related feldspar with a similar visual effect, the trade has accepted it as a legitimate gem in its own right. In practice, the industry has decided that the beauty of the light effect matters more than strict mineral labeling.
Why the Name “Moonstone” Sticks Anyway
Part of the confusion comes from how loosely “moon” names get used across different minerals. Selenite, for example, takes its name from the Greek word for moonshine, but it’s actually gypsum, a completely different and much softer mineral with no real connection to feldspar. Jewelers deliberately avoid calling selenite “moonstone” because gypsum is far too soft for durable jewelry, ranking only about 2 on the Mohs hardness scale.
True moonstone and rainbow moonstone at least share a real mineralogical relationship as feldspars, which is why the trade tolerates the shared name, unlike with selenite.
Why It Flashes Rainbow Colors
The glow inside traditional moonstone is called adularescence, a term that traces back to the Adula Massif in the Swiss Alps, one of Europe’s earliest known sources of the stone. The effect happens because the mineral forms with two slightly different feldspar types separating into thin, alternating internal layers as the crystal cools. Light entering the stone hits this layered structure, scatters, and bounces back out as a soft, billowy glow.
Rainbow moonstone works through a related idea, but its internal layering is different enough that instead of one soft glow, light breaks apart into a full spread of colors, blues, greens, purples, sometimes pinks, as you move the stone. This broader color-scattering effect is technically called labradorescence, tied to labradorite specifically, though many sellers still describe it as adularescence out of habit.
How Rainbow Moonstone Differs From Blue Moonstone
| Traditional Moonstone | Rainbow Moonstone | |
|---|---|---|
| Mineral | Orthoclase feldspar (adularia) | Labradorite feldspar |
| Optical effect | Adularescence (soft blue-white glow) | Labradorescence (multicolor flash) |
| Body color | Milky white or tan | Usually more transparent |
| Rarity | The classic, historically standard variety | Increasingly popular, especially in modern jewelry |
Traditional moonstone tends to stay more consistent in tone as you move it, a gentle blue sheen contained within a milky body. Rainbow moonstone is typically more transparent, with a bolder, wider, multicolor flash that shifts more dramatically as the stone tilts.
A Stone With Genuine History
Moonstone’s association with the moon isn’t a modern marketing invention, it goes back thousands of years across multiple civilizations. Ancient Romans believed the stone formed from solidified moonlight and connected it to Diana, their goddess of the moon. The Greeks used the term Aphroselene, combining the names of Aphrodite and Selene, to describe the stone’s light. In Hindu tradition, it’s known as chandra-kanta, meaning “moon loved,” and has long been considered a “dream stone” tied to visions and intuition.
These are cultural and historical associations rather than scientific claims, but they explain why moonstone has carried spiritual and symbolic weight across so many different societies for so long.
The Art Nouveau Connection
Moonstone had a genuine moment of high-fashion prestige during the Art Nouveau period in the late 1800s and early 1900s. The renowned jeweler René Lalique used the stone’s soft, glowing quality to complement the flowing, nature-inspired designs that defined the movement, favoring its subtle inner light over the sharper sparkle of faceted diamonds. This period cemented moonstone’s reputation as a serious jewelry material, not just a folk curiosity.
How to Judge Quality in Rainbow Moonstone
Flash strength. The best stones show a clear, easily visible color flash from multiple angles, not just one narrow viewing position.
Body clarity. A cleaner, less cloudy base makes the color flash stand out more sharply.
Cut. Rainbow moonstone is almost always cut as a smooth cabochon dome, since a flat facet scatters the light effect instead of showing it clearly.
Caring for Rainbow Moonstone
Rainbow moonstone ranks 6 to 6.5 on the Mohs hardness scale, noticeably softer than sapphire or ruby, so it needs more careful handling. Avoid ultrasonic or steam cleaners, since vibration and heat can damage the internal layers responsible for its color flash. Clean it gently with lukewarm water, mild soap, and a soft cloth, and store it separately from harder gemstones to prevent scratches. Also worth removing before swimming in chlorinated water or applying perfume and hairspray directly onto the stone.
The Bottom Line
Rainbow moonstone earns its name from a genuinely striking optical effect, even though it isn’t technically moonstone at all. Once you understand it’s really labradorite and know the real science behind its color flash, you’re in a much better position to judge quality and appreciate what you’re actually looking at.
A recent GIA GemNews update highlights a new find of high-quality rainbow moonstone from Madagascar featuring a rare orange flash effect.
For a complete overview of moonstone varieties, optical properties, and origins, visit the Wikipedia article on moonstone.
Learn more about colorless corundum properties and origins in the Root & Carat article on white sapphires.
