Published August 2011
by Jay Boyle, Sr. Gemstone Buyer
While many associate opal’s name only with those types that always display magnificent play-of-color, there is another beautiful opal variety that is often overlooked—Fire Opal. Fire opal gemstones glow with the fire of the volcanoes that spewed lava where they are produced so long ago: yellows, oranges and reds that are so bright you might think they would glow in the dark! While some fire opals can have the famous play-of-color so closely associated with the gem, they don’t need this phenomenon to captivate you. The most valuable fire opals are transparent and red, often called cherry opal because of their bright, bold colors. Ranging from transparent to translucent in appearance, fire opals have their own following in the world of gemstone collectors and aficionados.
Unlike most opals, fire opal is usually faceted so that you get sparkle in addition to vibrant color. Fire opal was born in fire in the ancient volcanoes of Mexico. It forms when water seeps into silica-rich lava, filling seams and hollows. Under heat and pressure, the silica forms a solid gel that traps the remaining water within its structure. Small pebbles of fire opal are found embedded in lava flows. Fire opal that displays play-of-color is rare because volcanic opal forms relatively quickly and the spheres of silica rarely have time to settle into the diffraction grids that create play-of-color.
Fire opal is mined in the Mexican states of Quéretaro, Hidalgo, Guerrero, Michoacan, Julisio, Chihuahua and San Luis Potosi. The most important mines are located in Quéretaro. Fire opal was discovered there in 1835 and some of the mines are still producing today. The state of Querétaro (pronounced ké re tar oh) is located in the central part of this vast country. From 1965 until 1975, there was a virtual “opal rush” at the Querétaro mines. It’s told by miners from that period that opals were so plentiful that they were sold by the sackfuls by thousands of miners in the area. As with everything, this prosperous time ended a short decade later and today opals of the same gem quality are much harder to find.
Like all opals, fire opal has a high water content. As a result, it should be protected from heat and prolonged exposure to strong light which could dry it out. If set into jewelry, fire opals are best worn in protective mounting designs. Gems can be cleaned with a mild soapy solution and water.
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