mineral

Fire Opal (in Matrix)

Hydrated Silica (SiO2·nH2O)

Hardness: 5.5-6.5 (Mohs scale); Color: Bright orange, red, or yellow body color; Luster: Subvitreous to waxy; Crystal structure: Amorphous (mineraloid); Cleavage: None (conchoidal fracture); Specific gravity: 1.9-2.3

Hardness: 5
Color: Bright orange, red, or yellow body color
Luster: Subvitreous to waxy

Identified March 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed from silica-rich groundwater filling cavities in volcanic rocks (typically rhyolite). Most fire opals were formed during the Tertiary and Quaternary periods in hydrothermal environments.

Uses & applications

Primarily used as a gemstone for jewelry (cabochons or faceted) and as a lapidary material for mineral collectors.

Geological facts

Unlike 'precious opal' which is known for its play-of-color, fire opal is valued for its intense body color. Mexico is the world's most famous producer, dating back to Aztec times where it was called 'Quetzalitzlipyollitli' (Bird of Paradise stone).

Field identification & locations

Identify by its translucent to transparent orange/red center nested within a lighter, often chalky or volcanic matrix (host rock). Commonly found in areas of past volcanic activity, specifically Jalisco and Querétaro, Mexico.