mineral

Blue-green opal cabochon (likely common opal)

Opal, hydrated amorphous silica (SiO₂·nH₂O)

AI-generated identification · may be incorrect

Hardness 5.5–6.5 Mohs; translucent blue-green body with orange coloration, vitreous-to-waxy luster, no cleavage, and amorphous (non-crystalline) structure. Its rounded polished cabochon shape indicates lapidary processing.

Identified September 2, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits hydrated silica in cavities, fractures, or volcanic rocks; many specimens are Cenozoic in age. The exact blue-green material may be natural opal, dyed opal, or treated common opal; the image cannot confirm origin.

Uses & applications

Used for cabochon jewelry, carvings, and mineral collecting; fine precious opal can be valuable, while common or treated opal is mainly ornamental.

Geological facts

Precious opal shows spectral play-of-color from microscopic silica spheres; this specimen appears to show body color rather than strong play-of-color. Opal can lose water and craze if exposed to heat or rapid drying.

Field identification & locations

Common sources include Australia, Ethiopia, Mexico, Peru, and the United States. Field identification relies on low hardness, lightweight feel, waxy luster, conchoidal fracture, and lack of crystal faces; UV, magnification, and treatment testing may be needed.