mineral

Green Common Opal

Hydrated Silica (SiO2·nH2O)

Hardness: 5.5-6.5 (Mohs scale); Color: Olive to pistachio green; Luster: Vitreous to waxy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 1.9-2.3

Hardness: 5
Color: Olive to pistachio green
Luster: Vitreous to waxy

Identified April 7, 2026More mineral →

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Physical properties

Hardness: 5.5-6.5 (Mohs scale); Color: Olive to pistachio green; Luster: Vitreous to waxy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 1.9-2.3

Formation & geological history

Formed at low temperatures from silica-rich waters that fill cavities in sedimentary or volcanic rocks. This specimen appears to be 'common opal,' meaning it lacks the 'play of color' (fire) found in precious opal.

Uses & applications

Used primarily as lapidary material for cabochons, carvings, and as decorative landscape stones or metaphysical 'healing' crystals.

Geological facts

Common opal is much more abundant than precious opal. Green common opal specifically often gets its color from inclusions of nontronite or other iron-rich silicate minerals.

Field identification & locations

Identify by its waxy luster and smooth, shell-like (conchoidal) fracture surfaces. It feels lighter than its size would suggest due to high water content. Common in volcanic regions with hydrothermal activity.