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Mexican Fire Opal

Mexican Fire Opal

“Psst, want to buy an opal?”
It’s not exactly what you’d expect to hear in the thronging tourist thoroughfares of Mexico City as one shops for souvenirs. But, believe it or not, this silicate is a common street corner commodity throughout the country’s tourist areas. And it has been so for years. Few Americans are ready for the sight of opal in profusion during their stays south of the border. That’s understandable, since this gem is associated with Australia. Nevertheless, while no rival to Australia in terms of production, Mexico has come into its own as an opal source. Indeed, the country’s opal is so distinctively different from Aussie material that it has earned its own name, fire opal, and its own following.

But don’t expect to be shown connoisseur-class material on Mexico City’s crowded sidewalks or even in its more private alleys unless you’re prepared to spend days looking.

Great Balls of Fire
At their best, Mexican fire opals possess either flaming-orange or cherry-red body color that is uniform and solid as opposed to the iridescent streaks, patches or flecks of color in fine Australian opal. That’s why use of the term “fire” with this breed of opal is a bit incongruous since it usually refers to play of color not, as in the case of Mexican material, to body color. In any case, if roughs are transparent or sufficiently translucent, they will be faceted rather than cut into cabochons.

This isn’t to say that Mexico doesn’t produce Australian-like color-play opal suitable for cabochon cutting, the standard cut with opal. According to a German cutter, top color-play opals from Mexico rival those from Down Under except that the Mexican variety, also known as “contra luz opal,” tend to array their colors against an orange background instead of a white one.
But when it comes to deep-body-color opals, whether cabbed or faceted, Mexican opal is distinctively different, with intense dayglo orange and red colors not seen anywhere else.

The Crazing Factor
Like all opal, the Mexican variety can crack in the course of time. What percentage of stones will be so afflicted is impossible to say. Fire opal specialists do not deny that crazing is a problem. But they quickly add that the problem is exaggerated. Further, they believe that they effectively circumvent it by subjecting stones to fairly intensive screening.
“First of all, we put stones on a mild heat radiator set at 80 degrees Fahrenheit for 10 days,” the German cutter says. “If problems develop, the stone is rejected.” If problems don’t emerge, that doesn’t mean the stone is out of the woods. The German cutter estimates that about 10 percent of the stones that make it past this initial heat test will start to crack up during the first stages of cutting, otherwise known as preforming. Tiny milky dots or larger spots are generally telltale signs that the stone could possibly go to pieces if kept on the wheel. The possibility that other cutters may not have been as careful is why buying street-corner opals isn’t such a good idea.

Mexican Fire Opal
Mexican Fire Opal