This is a sodium-rich plagioclase feldspar which displays a particular type of iridescence on a dark ground. The name labradorite is derived from its main source: Labrador, in Canada. The effect is probably due to the presence of very fine platelets of different compositions and minute inclusions of ilmenite, rutile and, perhaps, magnetite, which cause diffraction. '
Appearance The ground color is a dark smoke gray, but when light strikes it in a particular direction, it displays striking rainbow-colored reﬂections (violet, blue. green, yellow, and even orange and reddish) known as labradore scence. It is cut into gems, or small. not too convex, polished plaques for setting. It is also used as an ornamental material for carving and engraving. The background color is uninteresting and it is the strength of the labradore scence that gives the stone its value. The particularly brightly colored variety found in Finland is sometimes known as spectrolite.
Distinctive features It is highly distinctive at first sight butthere is an ornamental material, used in slabs and consisting of a rock containing large pieces of potassic feld spar, which looks similar to labradorlte. This material. which is called larvikite after the place where it is found in Norway, is used for building purposes only. it necessary, the two could be distinguished by their densities.
Occurrence The labradorite used in gems comes mainly from Canada and Finland.
Value Quite low, partly because it is hard to use. Few types of work can bring out its characteristic colors.
Simulents and synthetics It does not appear to have been imitated or produced synthetically.