Moonstone, a feldspar mineral, is recognized for its unique visual phenomenon. This article aims to guide readers in distinguishing genuine moonstone from imitations by focusing on its distinctive optical properties and other physical characteristics.
The Signature Glow of Moonstone
Moonstone’s signature feature is adularescence, a soft, shimmering light. This milky, bluish, or silvery glow appears to float just beneath the stone’s surface. Adularescence occurs when light interacts with microscopic, alternating layers of orthoclase and albite feldspar minerals within the stone. Light scatters between these ultra-thin layers, creating a luminous sheen that seems to emerge from within the gemstone.
To observe adularescence, gently move the stone under a direct light source. A genuine moonstone will display a mobile, shimmering light that moves across its surface as the viewing angle changes. This effect is distinct from a fixed internal shimmer, which does not exhibit the same depth or fluid movement. The quality of this effect often depends on the thickness and uniformity of these internal layers, with thinner, more consistent layers producing a stronger, more uniform glow.
Other Key Visual Features
Beyond its signature glow, moonstone exhibits several other visual traits that aid in identification. The gemstone’s body color can range from colorless, white, and gray to peach, pink, yellow, or blue. Moonstone ranges from semitransparent to nearly transparent.
Regarding clarity, moonstone commonly contains natural internal characteristics. These can include fine, thread-like structures known as “silk inclusions” or distinctive internal stress cracks, often referred to as “centipede-like inclusions,” due to their appearance. The presence of these natural inclusions can be a helpful indicator of authenticity, as perfectly clear stones may warrant closer inspection. To best showcase its adularescence, moonstone is most often cut into a smooth, domed shape called a cabochon.
Common Moonstone Impostors
Several materials are commonly mistaken for moonstone, and understanding their differences is important for identification. One frequent impostor is opalite, which is a man-made glass. Unlike natural moonstone, opalite often lacks internal inclusions and may even contain tiny bubbles from its manufacturing process. While opalite can have a milky or bluish appearance, its “glow” appears fixed or changes dramatically with the background or lighting, rather than moving across the surface with depth like true adularescence. Opalite also tends to feel lighter and may warm more quickly to the touch than a natural stone.
Synthetic spinel can mimic moonstone’s sheen, but it lacks the characteristic depth and movement of adularescence. Generic glass or plastic imitations are too uniform in appearance and do not display moonstone’s unique light-scattering properties. These materials may also feel warmer or lighter than genuine moonstone and can sometimes show visible mold lines or bubbles.