Sunday, 4 September 2016

Mexican Fire Opal

The traditional opal, with its unique play of color, has been valued since ancient times. During the Middle Ages, precious opal was regarded as especially lucky because it displayed the colors of many different gemstones. Not every culture has had the same views. A well-known Russian superstition associates precious opal with the evil eye.

Fire opal is an opal known not for its play of color, but for its vivid body color, which ranges from white to yellow to orange to red.

Like all opals, the fire opal is amorphous hydrated silicon dioxide. "Amorphous" indicates that opal has no crystalline structure; "hydrated" means that it contains water, typically from 3 to 10%. Opal is actually considered to be a kind of hardened jelly. But fire opal has some unusual characteristics not shared by other opals.

Opal is typically opaque and is cut en cabochon. Fire opal is the only kind of opal that can be transparent to translucent, and you will often find the higher-grade material cut in facets. People seeing these gems for the first time are often surprised to find out that they are opals.

Fire opal is associated especially with Mexico, and is mined in the Mexican states of Queretaro, Hidalgo, Guerrero, Michoacan, Julisio, Chihuahua and San Luis Potosi. The most important mines in Queretaro were discovered in 1835 and are still producing today.

Small quantities of fire opal can also be found in Oregon and British Columbia.