gemstone

Polished multicolored gemstone, likely boulder opal

Opal, hydrated amorphous silica (SiO₂·nH₂O), possibly ironstone matrix

AI-generated identification · may be incorrect

Hardness 5.5–6.5 Mohs; vitreous to waxy luster; translucent blue, red, and brown play-of-color; amorphous, with no cleavage. The vivid color flashes suggest precious opal rather than ordinary opal, though the small image prevents confident species-level identification.

Identified August 26, 2026More gemstone →

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At a glance

Common name: Polished multicolored gemstone, likely boulder opal
Scientific name: Opal, hydrated amorphous silica (SiO₂·nH₂O), possibly ironstone matrix
Category: gemstone
Identified: August 26, 2026
Method: Standard

AI Estimated Value

Approximately $10–$100 for a small common polished piece; $100–$1,000+ if natural, stable, and displaying strong multicolor play-of-color.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Opal forms when silica-rich groundwater deposits hydrated silica in cavities and fractures, commonly in volcanic or sedimentary host rock; formation is generally Cenozoic to Mesozoic depending on locality. The specimen appears cut and polished.

Uses & applications

Used in jewelry, cabochons, carvings, and mineral collections; boulder opal is especially valued when colorful opal veins contrast with dark ironstone matrix.

Geological facts

Play-of-color results from diffraction of light by regularly arranged microscopic silica spheres, not pigmentation. Opal can lose water and craze under severe drying or heat.

Field identification & locations

Common sources include Australia, especially Queensland and Lightning Ridge, plus Ethiopia and Mexico. Identify by colorful angular flashes, relatively low hardness, and absence of crystal faces; a loupe can reveal natural matrix and play-of-color.