It just so happens that approximately a dozen distinct classifications of minerals with hundreds of varieties exist in Mexico. As an example, the silicates class alone, contains more than 60 different minerals such as jadeite, zircon, topaz, and quartz, a subgroup of which includes amethyst. The carbonates class consists of bismutite, calcite, magnetite, dolomite, etc. while the sulfates class has gypsum, barite, cuprotungstite, etc.; many of these minerals being used for industrial applications. Finally, the mineraloids class which contains amber, obsidian, and opal; minerals that are frequently carved, ground, cut, and polished for objects of art, jewelry, etc.

Many of these minerals, including most opals, were formed during the Cretaceous period and brought to the Earth’s surface during the Pleistocene age. Of the 25 or so varieties of opals, the fire opal is the only naturally faceted opal and the most significant fire opal deposits are found in Mexico. One of the two largest sites for mining the Mexican fire opal, which just so happens to be the “national gemstone of Mexico”, is located near Magdalena, Jalisco; a small city located approximately 100 miles east of Vallarta that can be visited from PV during one of the ten hour day tours. Magdalena is in a region laden with igneous rocks, obsidian, volcanic lava, and more than 300 opal mines.

Mexican fire opals consist of silicon dioxide or silica spheres arranged in an orderly pattern with iron oxide dispersed throughout. It’s the iron oxide that gives the Mexican fire opal its distinctive brilliant flame-like colors of yellow, orange, and red. The three most important attributes of the fire opal are body colors, transparency, and play of color (differing colors when viewed from various angles). The greater the play of color, the more precious the gemstone. Because most opals are not faceted, they are generally displayed in the cabochon form. However, since fire opals are often found naturally faceted, they can be cut, polished, and mounted as cabochons or faceted stones. More...