Chemically, the Moonstone is opaque or translucent (but not transparent) variety of albite or feldspar, having a chatoyant reflection. It is not a hard gemstone (6/10 according to the Mohs Scale).
It occurs in white, gray, green, red and blue colors and many varieties of tints, where the blue dye is the most valuable.
The blue shine of Moonstone is caused by reflection from tabular crystals locating in parallel planes in the gemstone.
Superstitions attributed to Moonstone
Medieval sources tell us that the Moonstone is a remedy to improve memory. There is a belief that Moonstone held in the mouth could stimulate the activity of the brain.
The ancient treatises describe the usage of Moonstone as a remedy against epilepsy. The powder made of Moonstone presumably can attract the opposite sex. Therefore this gemstone symbolized a love charm. Moreover, this gemstone acquires its power gradually, according to the phases of the Moon.
As we know, our ancestors believed in the force of the Moon. Therefore, they endowed Moonstone with an ability to predict future. Thus, in the modern world, we think that Moonstone is a mascot for stockbroker, gamblers and other "gentlemen of fortune."
Moonstone for commercial purposes comes from Sri Lanka. Therefore, its old name was Ceylon Opal. But, in fact, its not Opal. Here, in Sri Lanka, it occurs in specimens of several inches in diameter.
However, there is so-called "moonstone brother" or "cousin." Its birthplace is the Adular Mountains of Switzerland, Switzerland, whence its second name "Adularia." But sometimes it bears the name "Sunstone."
Moonstone is an alternative Birthstone for June, along with the Alexandrite, whereas a Pearl is a principal Birthstone for June. As a Birthstone, it signifies the possession of good fortune and favor in love charms. The Moonstone is also appropriate for a Monday, according to a chart set by George F. Kunz.