Opal is a hydrated amorphous form of silica, with a high water content. It occurs in the fissures of almost any kind of rock.
Fire Opal is the name used for opal that is colored. It is not a name given because of a phenomenon. The gemstone cabochon may or may not have the rainbow flash, but it is a lovely color usually ranging from yellow, to orange, to red. The color of these gemstone cabochons comes from the presence of iron.
Opal fire flashing rainbow play-of-color is caused by diffraction of light by silica spheres stacked internally in the stone.
Fire Opal is mined in the Mexican states of Queretaro, Hidalgo, Guerrero, Michoacan, Julisio, Chihuahua and San Luis Potosi. However, the most famous source of Mexican Fire Opals is the state of Querétaro, where Fire Opal was first discovered in 1835 and is still be found today.
Rock strata containing opals run through the Mexican highlands, with their many extinct volcanoes. With a few exceptions, the gemstone, which lies hidden in cavities and crevices of Rhyolite, is extracted in open-cast mines. The work has left behind canyons with walls up to 20 feet high and deep passages which wind their way through the mining areas. Today, the Fire Opal is regarded as the national gemstone of Mexico.
These beautiful Mexican Fire Opals cabochons are cut in their rhyolite host material. This type of Mexican Fire Opal is sometimes referred to as a Cantera Opal. Most Mexican Fire Opal does not display the play-of-color. But ours does! The lovely phenomenon, of course, is best seen under bright light.
Metaphysical Properties of Fire Opal: It is said Fire Opal assist one in overcoming shyness. It can help make you feel more optimistic, socially outgoing, and confident.