Labradorite.
A sample of medium-grained, equigranular, light-grey anorthosite from Ten-Mile Bay, Labrador The stone has a unique appearance, as up to 20 percent of the labradorite crystals exhibit flashes of blue chatoyance on cut surfaces (the trade name is Reflect Blue). The deposit is marked by a black pyroxene-biotite foliation. Widely spaced joints and minimal fractures permit the extraction of large blocks. The deposit is located 10 kilometres south of Nain, Labrador, and is being developed by the Labrador Inuit Development Corporation, with help from an Italian company.

From Geological Survey of Newfoundland and Labrador - "Minerals of Newfoundland and Labrador - Industrial Minerals." http://www.gov.nl.ca/mines&en/geosurvey/. Courtesy of David Liverman, Government of Newfoundland and Labrador.