The question of whether Rainbow Moonstone is truly a variety of Labradorite is a common source of confusion for consumers entering the world of gemstones. This mineral identity crisis stems from the jewelry trade’s use of appealing names that prioritize marketability over strict scientific classification. While the term “Moonstone” typically refers to an entirely different mineral species, the widely sold Rainbow Moonstone is, in fact, a specific type of Labradorite. The relationship between these two stones is based on shared geological origins, but their visual presentation has caused them to be treated as distinct gems.
The Definitive Relationship: Rainbow Moonstone is Labradorite
Rainbow Moonstone is the trade name given to a variety of the mineral Labradorite, specifically one that is colorless or white in its base structure. Mineralogically and chemically, this gem is classified as a plagioclase feldspar, the same classification as traditional Labradorite. Their chemical composition aligns with that of Labradorite, making them the same species. This means “Rainbow Moonstone” is technically a misnomer, as true Moonstone is a different mineral—an orthoclase feldspar. Despite this technical inaccuracy, the name has been widely adopted by the gem trade to describe this white-bodied stone. The Gemological Institute of America (GIA) classifies this material as transparent Labradorite.
Shared Geological Identity and Light Phenomenon
The shared identity of Rainbow Moonstone and Labradorite places them within the plagioclase series of the larger feldspar mineral group. This series represents a solid solution between the sodium-rich end-member, albite, and the calcium-rich end-member, anorthite. Labradorite, including the Rainbow Moonstone variety, falls roughly in the middle of this series, containing a mix of both sodium and calcium aluminum silicate.
The characteristic flash of color seen in both gems is a result of light interacting with their internal structure, a phenomenon known as labradorescence. This optical effect arises because the mineral structure consists of microscopic, alternating layers of different feldspar compositions. When light enters the stone, it is diffracted and scattered by these ultra-thin layers, called exsolution lamellae, creating the iridescent spectral colors. Labradorescence creates a striking wash of color that appears to shift and move as the stone is turned. While some sources loosely apply the term adularescence—the soft, billowy glow seen in true orthoclase Moonstone—to the light play, labradorescence is the more accurate scientific term for the full spectrum effect.
Visual Distinctions and Commercial Naming
Despite being the same mineral species, the visual differences between traditional Labradorite and Rainbow Moonstone are the primary reason for their commercial distinction. Traditional Labradorite typically presents with a dark, smoky, or gray to blue-gray base color, often appearing opaque or translucent. The light flash in standard Labradorite usually appears as strong metallic-looking patches of blue, green, gold, or copper, often limited in the range of colors displayed.
In contrast, Rainbow Moonstone is characterized by a translucent to nearly transparent white or colorless body, allowing the light phenomenon to appear more ethereal and pronounced. This white background is specifically what allows the stone to display a wider spectrum of colors, including vivid blues, violets, and greens, which gives rise to the “Rainbow” part of its trade name. The commercial name “Rainbow Moonstone” capitalizes on the desirability of the white background and blue flash associated with true Moonstone, successfully appealing to consumers seeking a white gem with a vibrant, multicolored sheen.
Global Sources and Mining Locations
The geological conditions required to form plagioclase feldspars mean that both traditional Labradorite and Rainbow Moonstone are found across the globe, yet their primary sources are often geographically distinct. Traditional, darker-based Labradorite is historically associated with Labrador, Canada, where it was first discovered. Other significant sources for this type of material include Norway and Finland, where a high-quality variety known as Spectrolite is mined.
The more transparent, white-bodied variety known as Rainbow Moonstone is principally sourced from different deposits, most notably in India and Sri Lanka. Deposits in Madagascar and Australia also contribute to the global supply of Rainbow Moonstone. The specific trace elements and conditions present during the formation of these regional deposits likely influence the difference in base color and clarity, determining whether the resulting gem is marketed as standard Labradorite or the highly valued Rainbow Moonstone.