gemstone

Cantera Opal (Mexican Matrix Opal)

Hydrated silica in rhyolite host rock (SiO2·nH2O in Rhyolite)

AI-generated identification · may be incorrect

Hardness of 5.5 to 6.5 for the opal, 6 to 7 for the rhyolitic matrix; features pockets of vitreous, transparent to translucent fire opal and precious opal with play-of-color set within an earthy, swirling pinkish-brown to reddish-orange volcanic rhyolite; amorphous silica structure.

Identified October 3, 2026More gemstone →

Explore Cantera Opal (Mexican Matrix Opal) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in volcanic environments during the Tertiary period where silica-rich geothermal waters precipitated amorphous hydrated silica gel inside vesicles, gas pockets, and fissures of cooling rhyolitic lava flows and volcanic ash.

Uses & applications

Popular lapidary and ornamental stone carved into cabochons, polished eggs, freeforms, and spheres; widely used in jewelry settings and cherished by mineral collectors.

Geological facts

'Cantera' translates to 'quarry' in Spanish, referring to the traditional stone quarries in Mexico. Unlike Australian boulder opal which forms in ironstone or sandstone, Cantera opal uniquely forms within volcanic igneous rhyolite.

Field identification & locations

Identified by smooth, rounded or irregular translucent glass-like opal 'windows' (often displaying vivid flashes of color) embedded directly in a fine-grained, flow-banded reddish or tan volcanic rock. Sourced predominantly from Magdalena, Jalisco, and Querétaro, Mexico.