Mexican Fire Opal

raw fire opalChemical Composition: SiO2 nH2O hydrous silicon dioxide

Crystal Structure: Amorphous (non-crystalline) masses; kidney- or grape-shaped aggregates

Color(s): Translucent to deep red, anomalous double refraction, rainbow fireplay

Specific Gravity: 1.98-2.5

Mohs Hardness: 5.5-6.5

The warm color and fiery rainbows blazing inside the Mexican fire opal are most likely why the ancient Mesoamericans saw the precious stone as a symbol of ardent love. Both the Maya and Aztec cultures used it in rituals and art, calling it quetzalitzlipyollitli, or the ‘stone of the quetzal,’ a bird revered for its vivacity and goodness. Today it is known as the national gemstone of Mexico, and continues to be mined from the strata running through the now-dead volcanic mountains of the Mexican highlands.

Opals—known as “wet stones” because of their water content—are considered to be a kind of hardened jelly, which are formed when smoldering water from a volcanic eruption is instantly trapped inside silica rock and left to sit for millions of years. Traces of iron oxide in the mixture give the fire opal its distinct warm color, which can vary from yellow to orange to a rich cherry red. These unique tints make the fire opal the only kind of opal that can be found ranging from opaque to translucent.

The fineness of an opal depends on the clarity and richness of its color, as well as the depth of fire play in the specific gem. High-grade fire opals are most often seen as faceted, radiant gemstones fixed in formal jewelry, but they can also be cut as cabochons in matrix and used in a variety of settings.

Opal is fragile and prolonged exposure to heat or light can damage the gem, causing it to crack and cloud, or lose its fire play. Depending on where and how they were formed some opals can be naturally unstable and may cloud over time. Generally, the drier the place the opal is found, the more durable the stone. Our Mexican fire opals come from the famed opal mining municipalities in the state of Querétaro: Columbus, Tequisquiapan and Ezequiel Montes—places known for their hot, dry climate, and high-quality opals.