Rainbow moonstone is a specific variety of moonstone that displays a stunning, multicolored flash of light, often in shades of blue, purple, and even green. This effect is caused by the unique structure of the feldspar mineral, where layers of the mineral reflect light in a way that creates the appearance of a rainbow.

While moonstone typically has a milky or translucent appearance with blue or white adularescence, rainbow moonstone tends to have a clearer, more transparent body with more vibrant and varied flashes of color. The colors seen are a result of the diffraction of light, and the effect is often stronger when the stone is cut into a cabochon shape, which allows light to interact with the stone more effectively.

Rainbow moonstone is often used in fine jewelry for its striking visual appeal and is believed to have metaphysical properties similar to those of regular moonstone, including promoting emotional balance, intuition, and harmony.