What phenomenon is specifically caused by the scattering of light in some gemstones?

Adularescence is a phenomenon that arises from the scattering of light within certain gemstones, particularly within feldspar varieties like moonstone. This effect occurs when light interacts with layers of different refractive indices within the gemstone, leading to a soft, glowing appearance that often resembles a moving light source beneath the surface.

In contrast, chatoyancy, found in stones like cat's eye chrysoberyl, results from the reflection of light off parallel inclusions within the stone, creating a distinctive "cat's eye" effect. Opalescence, seen in opal, is caused by the diffraction of light due to the microscopic silica spheres within the stone. Fluorescence is a response to external ultraviolet light, causing some materials to emit visible light as a result of the energy absorption. Each of these other phenomena relates to different interactions of light with the material's structure rather than scattering alone, which is why adularescence is the correct choice for this specific question.