gemstone

Mexican Cantera Opal

Amorphous hydrated silica (SiO2·nH2O) in Rhyolitic host rock

Hardness: 5.5-6.5 on Mohs scale. Color: Translucent to transparent fire opal with play-of-color inside a pinkish-brown rhyolite matrix. Luster: Vitreous to waxy. Structure: Amorphous silica spheres.

Hardness: 5
Luster: Vitreous to waxy

Identified July 19, 2026More gemstone →

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Physical properties

Hardness: 5.5-6.5 on Mohs scale. Color: Translucent to transparent fire opal with play-of-color inside a pinkish-brown rhyolite matrix. Luster: Vitreous to waxy. Structure: Amorphous silica spheres.

Formation & geological history

Formed during the Tertiary period as silica-rich water seeped into cavities and vesicles within volcanic rhyolite flows, slowly solidifying into opal over millions of years.

Uses & applications

Primary use is in jewelry as cabochons, pendants, and rings. Also highly valued as a collector's specimen due to the contrast between the matrix and the opal gem.

Geological facts

The term 'Cantera' means 'quarry' in Spanish, referring to the volcanic quarry rock that serves as the host. Unlike many opals, Cantera opals are often stable enough to be cut with their host rock attached.

Field identification & locations

Identified by the distinct window of play-of-color opal surrounded by a matte, granular volcanic host rock. Major deposits are found in Queretaro, Magdalena, and Jalisco, Mexico. Collectors should look for vibrant flashes of red, orange, or green.

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