Moonstone, derived from a visual effect caused by light diffraction within the minerals microstructure consisting of multiple feldspar layers. Used in jewellery for centuries by the ancients, Romans and gGreeksand known for its pearly opalescent *schiller. Composed by to feldspars, orthoclase and albite and as these cool together they separate into alternating layers which reflect light creating *adularescence.
Albite crystallizes with triclinic pinacoidal forms. Its specific gravity is about 2.62 and it has a Mohs hardness of 6 - 6.5. Albite almost always exhibits crystal twinning often as minute parallel striations on the crystal face. Albite often occurs as fine parallel segregations alternating with pink microcline in perthite as a result of exolution on cooling.
*Adularescence is an optical phenomenon, similar to labradorite, that is produced in gemstones such as moonstones.
*Schiller, from German for "twinkle", is the metallic iridescence originating from below the surface of a stone, that occurs when the light is reflected between layers of minerals. It is seen in moonstone and labradorite and is very similar to adularescence and aventurescence.