Is Sunstone-Moonstone a Real Mineral?
Sunstone-moonstone is a trade name usually applied to a type of feldspar known as peristerite, particularly when it displays a blue or silvery sheen alongside warmer-toned internal reflections. It is not a natural combination of sunstone and moonstone.
The name has gained popularity within metaphysical circles; however, limited geological understanding and the widespread sharing of inaccurate information have led to the mistaken belief that sunstone-moonstone is a mineral in its own right, which it's not.
What Is Rainbow Moonstone?
Rainbow moonstone is a trade name most commonly used for white labradorite, a plagioclase feldspar that exhibits vivid flashes of blue caused by an optical effect known as labradorescence. Material sold as rainbow moonstone comes mostly from India and Madagascar.
The name is also sometimes applied to peristerite when it displays similar blue or silvery optical effects, although it's not as common.
Although white labradorite and peristerite are different feldspar minerals, they can look similar because both can produce a blue or silvery flash. However, this optical effect is produced by different internal structures.
Peristerite is composed of extremely fine intergrowths of feldspar minerals, which scatter light and produce a soft, diffuse blue or silvery sheen. White labradorite is a single feldspar mineral containing microscopic internal structures formed as the crystal cooled. These structures cause light to reflect internally, which produces a more distinct blue flash.
The term 'rainbow moonstone' is a perfect example of how trade names can create geological confusion.
Moonstone Versus Rainbow Moonstone
Moonstone is a variety of feldspar composed of orthoclase with thin layers of albite. Its characteristic glow, known as adularescence, appears as a soft, billowing sheen that seems to float just beneath the stone’s surface.
This optical effect is distinctly different from the flashes of colour seen in white labradorite and peristerite. True moonstone is typically white, cream, peach, or grey and has a smooth, silky lustre. When cut and polished, it looks completely different from material sold as rainbow moonstone.
Where Sunstone Fits In
Sunstone is a feldspar mineral known for its glittering optical effect caused by reflective, plate-like inclusions of hematite, goethite, or copper. This effect, known as aventurescence, produces flashes of orange, red, or gold as the stone is gently moved and is best seen in ambient light.
Sunstone–moonstone does not contain sunstone. However, some peristerite can display warm-toned internal reflections alongside a blue or silvery sheen, which can loosely resemble a combination of visual effects associated with sunstone and rainbow moonstone.
Despite this superficial similarity, sunstone, moonstone, white labradorite, and peristerite all form differently and owe their optical effects to different causes. Sunstone’s sparkle comes from metallic inclusions, while labradorite, peristerite, and moonstone display light-interference effects produced by internal feldspar structures.
Article Photos
The 'natural sunstone-moonstone' sphere, which is actually peristerite, is from a listing on an online marketplace.Pop-up photos: Peristerite: Courtesy of JR Montgomery (Mindat). White labradorite (rainbow moonstone): Courtesy of Géry Parent. Second white labradorite (rainbow moonstone): Courtesy of Giuseppe Pappa (Mindat)
The pink moonstone is from our collection.
