Moonstone – a gemstone with a pearly sheen

Moonstone – a variety of feldspar with an adularescence effect
Moonstone, also known as adularia, is a variety of feldspar with the chemical composition (Na,K)AlSi₃O₈. Its most striking feature is the optical phenomenon called adularescence – a fine pearly, bluish to silvery sheen that moves across the surface of the stone when light hits it, resembling moonlight.

Origin and location of moonstone
Moonstone is mined in various parts of the world – in India, Madagascar, Tanzania and Burma. However, moonstones from Sri Lanka are considered the rarest and highest quality, as they stand out for their intense blue adularescence and high transparency.

History and uses
Moonstone was valued in ancient times and in the Middle Ages was one of the popular precious stones of noble jewelry. In the 19th century, it became a sought-after gem of the Art Nouveau and Art Nouveau periods. Today it is valued both in jewelry and among mineral collectors.

Moonstone (adular) identification

Chemical formula: (Na,K)AlSi₃O₈

Color: colorless, white, bluish, yellowish

Typical effect: adularescence (pearlescent luster)

Crystal appearance: tabular, prismatic

Crystal system: monoclinic

Hardness: 6.0 – 6.5 (Mohs scale)

Luster: vitreous to pearly

Cleavage: perfect

Scratch: white

Density: 2.55 – 2.60 g/cm³