Labradorite

n. feldspar mineral which is generally bright blue or green in color

Labradorite ((Ca,Na)(Al,Si)4O8), a feldspar mineral, is an intermediate to calcic member of the plagioclase series. It is usually defined as having "%An" (anorthite) between 50 and 70. The specific gravity ranges from 2.71 to 2.74. The refractive index ranges from 1.555 to 1.575. Twinning is common. As with all plagioclase members the crystal system is triclinic and three directions of cleavage are present two of which form nearly right angle prisms. It occurs as clear, white to gray, blocky to lath shaped grains in common mafic igneous rocks such as basalt and gabbro, as well as in anorthosites.
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n. labradorite, type of mineral

n. labradorite, feldspar mineral which is generally bright blue or green in color

(n.)
A kind of feldspar commonly showing a beautiful play of colors, and hence much used for ornamental purposes. The finest specimens come from Labrador. See Feldspar.