Moonstone Sources and Imitations
Translucent, adularia moonstone is most often found in the form of water-worn pebbles that have eroded from pegmatite masses. In most mining locations, these gravels have formed layers between rock and dirt and the material needs to be shoveled and hauled to a rushing water source, like a sluice or a river. Here the dirt is placed onto screens so the dirt can be washed away and the moonstone bits can be separated from the remaining debris. Needless to say, good quality moonstone is rarely found in a size that might be called large.
The most popular "mines" I mention above are located in the countries of Sri Lanka, Burma, and India, where moonstone is found in the pastel shades of pink, yellow, green, and white. North American areas include Ontario, Canada, and Virginia, and in New Mexico, sanidine moonstone is a special find. Moonstone is also found in Switzerland, Madagascar, Brazil, Kenya, and western Australia.
The most common imitation for moonstone is glass, usually a type of glass known as opalite. Chatoyant chalcedony can also be mislabeled as moonstone. You probably should also know that because the word selenite comes from the Greek word relating to the moon, some people think moonstone can also be called selenite but selenite is a totally different mineral belonging to the gypsum group, and not the feldspars.
A pair of calibrated peach-tone moonstone cabochons. Private collection, Dale Armstrong.