Information on Opals

Chemical Makeup

• The colorful play within opals is due to tiny spheres of silica, which dissect light on its way through the gem, causing a constantly changing scene. Opals are actually not stones; rather, they are a gel made of silica and different percentages of water (between 2 percent and 6 percent). If these gems lack any opalescence, they are known as "common opals."

Australian Opal

• There are many types of Australian opals. Depending on the background color, the types are dark or black opal (black or dark gray with all colors, considered the finest of all opal); white or light opal and milk or crystal opal (white or light with all colors); boulder opal (brown with blues); opal matrix (brown with greens and golds); and Yowah nuts (the "picture stone"). About 95 percent of all fine opals hail from the Australian outback. The value of the stone is based on its transparency, translucence and opacity; the play of color; the colors themselves, and the pattern in the gem; and the gem's thickness.

Fire Opal

• Fire opal is another type of opal and was discovered in Mexico. These opals are transparent red, radiant orange or yellow, and they consist of silicic acid and water. Fire opals are also found in other countries, but the only other fine fire opals are mined in Brazil. The color comes from trace amounts of iron oxide, and the the stone's durability depends on the dryness of the area where it was found.

History

• In 1849 the first opal block was discovered by chance on an Australian ranch, and opal prospectors began to mine there in 1890. Opal came into vogue in America during the Art Deco era of the 1920s through the 1940s, where they were paired with enamel, one of the most popular jewelry materials of the time.

Warning

• Because of the water in opals, they can easily become damaged due to dryness. If they are exposed to heat for a long time or stored in too dry of a space, opals develop small breaks and the colors within will become paler. So wear them often, because they will benefit from moisture in the air and from the wearer's skin.