Moonstone

Moonstone, also known as Hecatolite, is an aluminum, potassium, sodium, silicate (alkali), feldspar mineral, and variety of Orthoclase (with Albite inclusions). Its name was derived by A. G. Werner in 1780 due to the shimmering effect that occurs on the stone’s surface during light diffraction. This has made Moonstone extremely valuable in the jewelry world thus resulting in high prices.

There are quite a few Moonstone localities in the world, although the highest quality material (adorned by jewelers) is usually from Sri Lanka, India, Brazil, Myanmar, Australia, and Madagascar. Large, mechanized moonstone mines do not exist. Instead, most production is from artisinal mining. The miners prospect through stream sediments and gravels where moonstone is found, often along with a variety of other gems. A smaller amount is mined underground, where miners dig into soft kaolinite clay that developed as a residual material above weathering feldspar deposits and igneous rock masses.

Adularescence is observed in pieces of feldspar that contain thin alternating layers of orthoclase and albite. These micron-thick layers of different composition also have different refractive indexes. Light, penetrating one layer after another, is bent, reflected and scattered at the surface of each layer. The scattered light within the stone is what causes the adularescent glow and the beauty of the gem. An even rarer occurrence is moonstone that exhibits a spectrum of iridescent colors.

These specimens are known as "rainbow moonstone". This phenomenon occurs when white light is separated into its spectral colors while passing through the stone. The feldspar mineral labradorite is usually the source of these iridescent colors. Oddly enough, moonstone is also the state gem of Florida. That has more to do with Cape Canaveral’s moon launch, however, rather than due to deposits of it in the state.

Despite the proclamation, Florida remains bare of moonstone deposits.