Natural Blue Fire Labradorite Faceted Oval Shape Nuggets Beads 15 inches strand and Size 6.5 to 7.5mm approx. Labradorite a feldspar mineral, is an intermediate to calcic member of the plagioclase series. Labradorescence is a side-effect of the molecular change which occurs in large crystal masses of anorthosite, producing an iridescent play of colors.