The name opal was probably derived from Sanskrit "upala", meaning "valuable stone".
Moss opal belongs to the category of "common
opal", which is opaque, rarely translucent, and typically exhibits no play of color. Precious opals display rainbow-like hues that change with the angle of observation. Moss opal is a milky white opal with unique inclusions of green hornblende in moss-like patterns. They are also often traded under marketing names, such as '
dendritic opal' or 'tree
agate'. Moss opals are mostly offered as
opal cabochons and are best suited for earrings, brooches, and pendants. Other types of opals that are trade with matrix or host rock (e.g.,
boulder opal and
opal in matrix) are more durable and are better suited for rings. Even though opals are quite fragile, they are still one of the world's
most popular jewelry gemstones.
There is a long standing belief in the healing power of opal. It is reported to be able to relieve depression and to help its wearer find true love.
Opal is one of the official
birthstones for those born in October.