moonstone is a form of felspar, and comes chiefly from Ceylon. There it
occurs in large pieces in clay. When properly polished the gem exhibits
a beautiful pale-blue light coming from within. The cause of this light
is hard to explain, but is thought to be a reflection from minute
tabular crystals arranged in parallel position in the stone. Moonstone,
like most of the more or less opaque gems, is usually cut cabochon
form. The stone is now becoming more and more popular.