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Albite moonstone
The sodium-rich end-member of the plagioclase
feldspar group, called albite, from the Latin albus, because
of its whitish color, may look similar in appearance to adularir
moonstone if cut en cabochon. Furthermore, in both cases the
composition is midway between that of orthoclase anC that
of albite: albite moonstone can, in fact, be defined as 2
microperthitic association of albite and orthoclase with a
predominance of albite. For this reason, it is considereo
acceptable to use a similar name for the two gems.
Appearance It is typically
misty, semitransparent or semiopaque with a pale, shimmering
reflection, less well defined than in chatoyant stones. It
may be milky white in color, or dull yellow, yellow-gray or
greenish gray. It is almost always cut en cabochon. Curved
pieces are also cu* as necklace beads or pendants.
Distinctive features The adularescence is
quite distinctive. This is also found in adularia moonstone,
but the twc are distinguishable by their density, which is
higher (from about 2.62 to 2.65 g/cm3) in albite moonstone.
The refractive indices, which are always hard to establish
in curved stones, are slightly higher (na 1.525, rty 1.53•
than those of orthoclase, with slightly stronger birefn gence
as well. The yellowish or light brown coloration some specimens
also distinguishes it from adularia moo stone.
Occurrence It comes mainly from Canada and Kenya b occurs
also in India and Sri Lanka. In the latter two countries,
however, it is confused with the similar variety of r. thoclase.
Value Somewhat low, like adularia moonstone.
Simulants and synthetics It is imitated by
milky sy thetic spinel, which, however, (virtually) lacks
the mob reflection. It is not manufactured synthetically.
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