The small state of Queretaro, in the Central region of Mexico, has numerous touristic gems: its colonial capital, Queretaro, with its elegant string of stately plazas; the quintessentially quaint town of Bernal that lies in the shadow of the Pena de Bernal, the world’s third largest monolith along with my favorite antojitos/masa-based snacks, blue corn gorditas; the “thermal spring” town of Tequisquiapan bejewelled with purple bougainvilleas; the lovely mountain town of Jalpan, gateway to the Sierra Gorda Missions and to the Sierra Gorda Biosphere Reserve. Yet, the most lustrous of Queretaro’s gems is the opalo de fuego/fire opal, regarded to be the national gemstone of Mexico. Queretaro is the world’s largest producer of this iridescent volcanic natural wonder.
Called vitzitziltecpal (hummingbird stone) by the Aztecs and quetzalitzlipyollitli (after the strikingly colorful bird, the quetzal) by the Mayans , fire opal was utilized by the Aztecs and Mayans for both ritualistic and ornamental purposes-oftentimes, artistically set in mosaics. With the onset of the Spanish conquest of Mesoamerica in 1519, due to the Spaniards’ monomaniacal quest first with gold, then with silver, the fire opal was totally ignored by the conquistadors and all of the original mining locations were eventually “lost.” It was not until the mid-1800’s that this gemstone was “rediscovered.”
That rediscovery occurred in Esmeralda, Queretaro. Now, the three principal opal producing regions of the state are the municipalities of Tequisquiapan, San Juan del Rio and Colon. There are approximately 100 mines in those three regions and the majority are currently closed. The oldest mine, Santa Maria del Iris, which has produced the finest quality and highest quantity of fire opal, has opened and shut 28 times. The late 1960’s and early 1970’s was the peak period of opal production. Ten other Mexican states have fire opal mines. The majority of the fire opals are exported to the US, Canada, and Western Europe, with the best quality gems going to Japan and Hong Kong.
Fire opals are mined in open pits in ancient volcanic lava flows. The mined opals in Queretaro are imbedded in a matrix of rhyolite, specifically cantera. Cantera is the quarried pink rock that many of Mexico’s colonial buildings were fabricated from; the colonial “pink” edifices in the historic city center of Morelia, Michoacan being an example of this.
Geologically speaking, iron oxide is responsible for the fire opals brilliantly distinctive flame-like colors of yellow, orange, yellow-orange, red, or red-orange. Fire opals range from translucent to transparent, the most preferred. The vast majority of fire opals are classified as semiprecious as they do not exhibit a play of color (which means differing flashes of color when the gem is held at varying angles); the few that demonstrate a play of color are termed precious. Deep rich red-orange opals that have the highest degree of clarity and transparency are the most desirable and valuable of the semiprecious variety.
Once mined and sorted, sold by the carat, fire opals can be cut, polished, and mounted, either as cabachons or faceted gems. In fact, due to its unique physical qualities, of the 25 kinds of opals found throughout the world, only the fire opal can be faceted. Opals that cannot be cut, due to their small size or irregular shape, may just be left in the polished (or rough) cantera matrix or the cantera may be carved into various shapes and designs; such pieces can be stunning as the brilliance of the iridescent opal is framed in the darker pinkish material.
Fire opals, unike diamonds, rubies, emeralds, or sapphires, are a soft and fragile gemstone; the finished gem is best suited for earrings, pins, pendants, or tie tacks. Fire opal rings must be protectively encased to ensure that the stone does not get damaged. Like all opal, fire opal has a high water content. Consequently, they must be shielded from prolonged exposure to heat and intense light as the gemstone may dry out, potentially resulting in cracks.
In the city of Queretaro, you can see rough and finished pieces of fire opal in various locations: in jewelry stores (most have them displayed in bottles of water- please, keep in mind and wallet that these are not of the highest quality, attractive as they may be!); in rock /mineral shops; and in some kiosks that are in the pedestrian shopping areas. Also, I have seen (and purchased, of course) inexpensive samples of non-precious opal embedded in large pieces of cantera in the artisan market in Tequisquiapan . The last time in I was in Queretaro City, I purchased from one of the kiosk vendors a small, lovely non-precious yet sparkling multi-colored opalo that I made into a pendant for myself. Tours to opal mines are available and can be arranged in Queretaro city or Tequisquiapan.
Queretaro is justifiably proud of being the world’s largest producer of the finest specimens of Mexico’s national gemstone. Quality opalos de fuego are a sight to behold! The state of Queretaro, about half the size of New Hampshire, is a delightful place to experience its magnificent fire opals, and, not to forget, its non-mineral touristic gems.