Rainbow Moonstone Sterling Silver PendantTurn it in the light and a blue flash crosses the surfaceone of the stranger optical effects in mineralogy. Rainbow Moonstone is white labradoritea plagioclase feldsparwhose adularescence is produced by light scattering between alternating thin layers of feldspar with slightly different compositions. The blue sheen that drifts across the surface is not a color in the stone itself; it is an interference effect, the same physics that produces color in