It is increasingly difficult to find specimens with strong colour—this is an exemplary labradorite specimen.

Labradorescence is a side-effect of the molecular change which occurs in large crystal masses of anorthosite, producing an iridescent play of colours. This labradorescence, or schiller effect, is the result of light diffraction within the lamellar intergrowths – fine, adjacent layers of the separate materials (lamellae) comprising the whole rock phase – created when conditions do not allow for sufficient diffusion to the materials' equilibrium composition.