is a plagioclase feldspar that shows remarkable iridescence in the form of a schiller or metallic luster when the light hits the stone from particular angles. This iridescence is termed "labradorescence" and is thought to be caused by fine platelets of varying composition and minute inclusions that diffract the light. Spectrolite is a trade name for a rare labradorite
from Finland that exhibits the spectral colors. Some spectrolite gemstones will show violet, blue, green, yellow, orange, and red iridescence.