Raw moonstone chunk

Price is for 1 The name moonstone derives from the stone's characteristic visual effect, called adularescence (or schiller), which produces a milky, bluish interior light. This effect is caused by light diffraction through alternating layers of orthoclast and albite within the stone. The diffracted light varies from white to blue, depending on the thinness of the albite layers.[1] More technically, this micro-structure consists of regular exsolution layers (lamellae) of different alkali feldspars (orthoclase and sodium-rich plagioclase). Polished moonstones often display chatoyancy ("cat's eye" effect), where a luminous streak appears through the stone. Asterism is rare and produces four-legged stars.[1] Geology[edit] The most common moonstone is of the orthoclase feldspar mineral adularia, named for an early mining site near Mt. Adular in Switzerland, now the town of St. Gotthard.[1] A solid solution of the plagioclase feldspar oligoclase +/− the potassium feldspar orthoclase also produces moonstone specimens. Deposits of moonstone occur in Armenia (mainly from Lake Sevan), Australia, the Austrian Alps, Mexico, Madagascar, Myanmar, Norway, Poland, India, Sri Lanka, and the United States.[2][3] Historically, the most valuable, transparent moonstones with strong blue sheen came from Myanmar.[1] Today, most commercial moonstones come from Sri Lanka.[3]