The Schiller effect, or adularescence, is a variable optical phenomenon exisisting in gemstones and in minerals.
This effect is usually seen just below the surface in certain varieties of gems and minerals as in some pyroxenes and feldspar.
It comes from a milky to an almost metallic shimmer to a vivid iridescent play of colors.
It is the result of thin inclusions refracting and reflecting with incident light.
The Labradorite, a plagioclase feldspar, usually shows a very pronounced iridescent schiller effect.
