The enchantment of a moonstone is when light falls between its thin layers, scattering in many directions, producing the phenomenon called adularescence. Adularescence is the light that appears to ripple across a gemstone, giving its surface a glowing appearance. Moonstones display a much softer glow in comparison to the rainbow moonstones which typically have brighter blue flashes in them.
Moonstones are often used as an alternative to pearl and alexandrite as a birthstone for June.
While Moonstone and Rainbow Moonstone are related there is a bit of difference to the gems. Moonstone is Orthoclase Feldspar (derived from calcium sodium) while Rainbow Moonstone is a Plagioclase Feldspar (derived from potassium sodium), which is the same chemical composition for Labradorite. Rainbow Moonstone can often contain Black Tourmaline inclusions and despite the name a Rainbow Moonstone is in fact a White Labradorite.