gemstone

Opal cabochon

Opal, hydrated amorphous silica (SiO₂·nH₂O), likely common or Ethiopian precious opal

AI-generated identification · may be incorrect

Hardness 5.5–6.5 Mohs; translucent milky blue-white body with orange-red play-of-color, vitreous to waxy luster, no cleavage, amorphous structure, and specific gravity about 2.0–2.2. The smooth domed shape indicates a polished cabochon.

Identified September 4, 2026More gemstone →

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At a glance

Common name: Opal cabochon
Scientific name: Opal, hydrated amorphous silica (SiO₂·nH₂O), likely common or Ethiopian precious opal
Category: gemstone
Identified: September 4, 2026
Method: Standard

AI Estimated Value

Approximately $10–$100 for a small common or treated cabochon; $50–$500+ for attractive natural precious opal, depending strongly on brightness, pattern, clarity, and origin.

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 gel in cavities and fractures, commonly in volcanic or sedimentary host rocks; most gem opal is Cenozoic, especially from Australia, Ethiopia, and Mexico. The image cannot establish locality or whether the color is natural, treated, or synthetic.

Uses & applications

Used primarily in jewelry and mineral collections; cabochons are favored because opal is not suited to faceting and is relatively soft. It has little industrial use beyond specialty silica materials.

Geological facts

Play-of-color results from diffraction through regularly spaced microscopic silica spheres; orange flashes indicate warm spectral colors. Some opal can craze or crack with drying, heat, or sudden temperature changes.

Field identification & locations

Identify by its low hardness, light weight, waxy appearance, and moving spectral flashes; glass imitations usually show bubbles or a columnar mosaic pattern. Common sources include Lightning Ridge and Coober Pedy, Australia, Welo, Ethiopia, and Jalisco, Mexico.