Moonstone is a potassium feldspar of the orthoclase (adularia) species with white shimmer, similar to moonshine (therefore the name) adularescence. It is a member of the feldspar group of gems. It can be transparent with a strong blue schiller on the surface; or it can have a striking cat’s eye or star effect. Moonstone’s shimmer is distinctively blue. If the sheen displays in a variety of hues, the stone is known as “rainbow moonstone,” which is actually a variety of labradorite, another type of feldspar.
Moonstone can be colorless, yellow, with iridescent pale sheen, blue or pink. Its luster is vitreous to silky. It occurs in pegmatites and in placers. Each locality may have characteristic inclusions.
In Sri Lanka moonstones usually have straight lathlike “stress cracks” which run parallel to the vertical axis of the crystal and from which they are branching cracks which appear to taper off. It is found in dikes or in water-worn pebbles in the gem gravels. Moonstone from Sri Lanka is considered the best and it is sometimes referred to as the National Stone. Indian moonstone is characterized by the variations in body color from white to reddish brown, or plum-blue, and even green. Indian moonstone has been considered a sacred stone in India, where it is often believed to be moonlight in a magical, solid form.
Moonstone was also popular in the Art Nouveau jewelry of the early 20th century, and presently it is again in demand. It is rare which makes it reasonably expensive. In addition to its beauty, moonstone is believed to possess strong protective and healing powers.
Moonstone can be found in Sri Lanka, Burma (Myanmar), Brazil, India, Madagascar, and the United States.
Moonstone is usually confused with chalcedony, synthetic spinel, and glass imitations.
Mohs’ Hardness: 6 – 6 ½