What Is Sunstone? The Sparkle Is a Different Effect Than Moonstone's

Sunstone belongs to the same broad feldspar family as moonstone and labradorite, but it produces a third, distinct optical effect called aventurescence. Rather than moonstone's soft floating glow or labradorite's sharp color flash, sunstone's sparkle comes from thin, flat platelet inclusions of copper or hematite scattered through the stone, which catch and reflect light like countless tiny mirrors.

The effect is strongest when the stone is cut to align with those internal platelets. Oregon, where sunstone is the official state gemstone, produces material with naturally occurring copper inclusions; other sources include India and Norway.