Labradorite was named for Labrador in Canada, but the vast bulk of commercial material is from Maniry in the Southern Madagascar. It's a plagioclase feldspar and displays a beautiful colour play - a schiller effect called labradorescence. This is due to light refracting from the interlocking platy crystals that form the mineral. A white form of the same mineral is called moonstone. Both are commonly used for jewellery now.
These pieces are polished pebbles.