Why the Strut? I Am the Peacock of the Gem World

A PEACOCK WITHOUT ITS feathers is just a pheasant. Likewise, if it were not for the full spectrum of iridescent colors I show against a black velvet base, I would just be labradorite. After being accidentally discovered in Finland during World War II, I became the center of a considerable local industry in the cold far north of that white land. Supplies have since dwindled, but you will still find me in earrings and pendants, often at art shows and on Etsy.

Who am I?