Opal

Opal is a gemstone that ranges from semi-transparent to opaque. Opal's body color covers a broad spectrum of colors, but it is mostly prized for what is known as 'play of color.' This is the ability to reflect and break up light into multiple colors which occur as medium- to broad-sized pinpoints, or larger flashes within the stone. Play of color occurs in only a fraction of Opal stones, and the rest of the non-precious opal is known as potch.

Opal was formed when silica was liquefied and washed down into fissures in the surrounding rock, where it then solidified into a hardened gel. Unlike most other gemstones, Opal is therefore not a crystal, but rather an amorphous solid. Microscopic silica spheres sometimes would line up in a pattern which acts as a diffraction grating, which has a prism like effect and produces the brilliant plays of color.

Opal today is mostly found in Australia, Mexico, and the USA. Its name comes from the Sanskrit "Upala" and the later Greek derivative "Opallios," meaning to see a change of color. There are several types of naturally occurring opals:

White Opal: A transparent or white body color with play of color.

Black Opal: Blue, grey, or black body color sets off the play of color.

Fire Opal: Yellow to orange body color: may have play of color or if not, is often fashioned into faceted stones.

Boulder Opal: Most often black Opal which has occurred in thin veins; the resulting cut stones have a layer of Opal with some of the ironstone matrix still intact.

In addition to these completely natural stones, stonecutters create some assembled Opal gemstones:

Opal Doublet: A thin slice of Opal is glued to a black or brown backing stone to enhance its color and makes it durable enough for wear.

Opal Triplet: Same as an Opal doublet, but with a clear quartz or glass cap added on top of the Opal for added durability. The slice of Opal used in the triplet is often much thinner.

The ancient Romans called Opal the queen of gems because it encompassed the colors of all the other gems. They revered Opal as a symbol of hope and purity and held it to be second only to the prized Emerald. At that time Opal, called by the Latin "Opalus," was primarily found in India. In later times, women in Scandinavian countries wore opals as hair ornaments in the belief that it preserved their blond hair and kept it from going grey.

The Arabs thought that opals were formed by lightning strikes and that this is why the brilliant flashes of color are captured within. Other legends said that Opal would act to ward off lightning, and give the cloak of invisibility to its wearer when desired. It was supposed to grant vigor, aid the heart and kidneys, and protect against fainting and infection.

A modern folktale, in which a person should not wear Opal unless it is either their birthstone or a gift, traces its roots to the 1817 novel by Sir Walter Scott, "Anne of Geierstein," in which Opal is associated with misfortune borne by the heroine.

Opal should be treated with some care to prevent sharp blows, scratches, and should never be kept in oil or other chemicals. Opal contains a percentage of water as part of the stone; it need not be kept in water, but should never be stored in a bank vault for long periods of time because of the dehumidifiers used in many vaults. Hardness: 5-6.5

Toughness: poor to fair

Birthstone: October (along with pink tourmaline)