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144 PRECIOUS STONES
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LABRADORITE
Is so named because it was originally from Labrador.
It is a feldspar; and is found on the coast of Labrador, Finland, Russia, and the United States.
Crystallization triclinic; usually in cleavable masses.
Hardness, 6; specific gravity, 2.7.
Lustre
vitreous to pearly; translucent to opaque; some specimens show an
iridescent chatoyancy and play of blue, green, golden-yellow, and red.
Cleavage, one direction perfect; one imperfect.
Composition: silica, 53 ; alumina, 29; lime, soda, etc., 18.
Fuses with difficulty before the blow-pipe, and is decomposed with muriatic acid.
Body
color, gray, brown, or greenish brown, in which prismatic hues appear
if the stone is polished flat and parallel to the reflecting surfaces.
This is due to minute particles of oxide of iron distributed throughout
the body of the stone. These are not always present.
Other forms of feldspar not used as jewels are lennilite, elaeolite, albite, perthite, peristerite, leopardite, and pitch-stone.
Albite and peristerite often show considerable chatoyancy, and are called " moonstones" in the localities where they are found.
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