La Trinidad Fire Opal Mines
The most significant deposits of Fire Opal were discovered in Queretaro, Mexico in 1835, and are still producing today.
There’s a small picturesque town in the state of Queretaro, called Tequisquiapan, which is the geographic center of Mexico. Around 30mins from it you find an even smaller town called La Trinidad (The Trinity), a place surrounded by mountains and cacti trees and home to the Fire Opal Mines.
Fire Opal its distinguished by its red, yellow and orange hues. Mayans and Aztec cultures named them “Quetzalitzlipyollitli“, which means “Stone of the Bird of Paradise”. Today Mexican Fire Opal is considered the National Stone of the central American state.
Opals are formed in the depths of ancient volcanoes, due to the incredible heat and pressure, the lava keeps water within itself and thus forming these sun-bright stones.
The mining of opals in La Trinidad is the main economic activity of the entire town; stores and a few tour guides, who are the owners of the mines, sell the opals they have found throughout the years, raw, polished or set in jewelry, they take you to the mines were you can hammer, chisel and crack rocks to try your luck.
The gemstone, which is hidden in cavities and crevices, is mostly found in open-cast mines and labyrinthine passages through the mining areas. Miners use hammers of all sizes, chisels and picks to extract all opals by hand, a very labor intensive and time consuming job, as is done the same way it’s been done through generations.
Some opals are found married to the stone where they are found and instead of risking the opal to break when extracting it, it is cut and polished within the stone around it to keep its form intact, this is called Opalo Cantera meaning Matrix Opal.
The drier the place where opals are found, the more durable they are.
Fire opals in Mexico have a low water content in relation to opals found in other places of the world, so this makes them more resistant.
One way to know the quality of an opal is dropping it in water, low quality opals will have a matte and dull color and higher quality opals will show a more bright color, this will also determine if the opal will change its color and transparency over time.
References:
Personal visit to La Trinidad Opal Mine
https://agta.org/education/gemstones/fire-opal/