A microperthitic association of orthoclase and albite (with a predominance of orthoclase). Because of its slightly turbid transparency. gems cut en cabochon show a mobile reflection, which is softer and more diffuse than that of chatoyant stones.
Appearance Moonstone generally has an almost transparent ground, which is practically colorless. palegray. or tinged with yellow, with a whitish to silvery white or blue shimmer. It is normally cut into cabochons or curved pieces tor threading into necklaces. etc. Incipient cleavage cracks may be visible inside the stone.
Distinctive features Adularescence (a slight turbidity with a mobile reflection) is in itselfdistinctive. Another feldspar. albite, can look identical (for the same reason) and is also called moonstone. If necessary, the two may be distinguished by their density. which is lower in orthoclase. An imitation form consisting of synthetic spinel is much milkier in appearance. without a mobile reflection.
Occurrence Adularia moonstone is found mainly in SriLanka. Burma. India. Australia, Madagascar, Tanzania. the United States. and Brazil.
Value Fairly low, but the type with a blue reflection is quite highly prized.
Simulants and synthetics It has been imitated by milky synthetic spinel. which does not have a proper mobile reflection. lt has not been manufactured synthetically.