June’s third birthstone, moonstone, was named by the
Roman natural historian Pliny, who wrote that
moonstone’s shimmery appearance shifted with the
phases of the moon.
The most common moonstone comes from the mineral
adularia, named for an early mining site near Mt.
Adular in Switzerland that supplied this gemstone.
This site also birthed the term
adularescence, which refers to the stone’s
milky glow, like moonlight floating on water.
Moonstone is composed of microscopic layers of
feldspar that scatter light to cause this billowy
effect of adularescence. Thinner layers produce a
bluish sheen and thicker layers look white.
Moonstone gems come in a range of colors spanning
yellow, gray, green, blue, peach and pink, sometimes
displaying a star or cat’s eye.
The finest classical moonstones, colorlessly
transparent with a blue shimmer, come from Sri Lanka.
Since these sources of high-quality blue moonstones
have essentially been mined out, prices have risen
Moonstones are also found in India, Australia,
Myanmar, Madagascar and the United States. Indian
gemstones which are brown, green or orange in
color are more abundant and affordably priced than
their classical blue counterparts.
This beautiful gemstone’s weakness is its relatively
low hardness of 6 on the Mohs scale, making it prone
to stress cracking and cleaving. Care is required
with moonstone jewelry like rings or bracelets; so sometimes brooches and pendants are preferred for long term durability.