Labradorite is a feldspar mineral and is soft grey/blue stone with lustrous blues and greens flashing inside it. Also called spectrolite, it is named for Labrador, the Canadian peninsula where it was first found in 1770. Labradorescence is a side-effect of the molecular change which occurs in large crystal masses of anorthosite, producing an iridescent play of colors similar to adularescence. 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. Gemstone varieties of labradorite exhibiting a high degree of labradorescence are called spectrolite.

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