mineral

Polished chalcedony (likely carnelian or brown agate)

Microcrystalline quartz, SiO₂; chalcedony variety with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent brown, honey, and reddish zones with a waxy to vitreous luster. Cryptocrystalline quartz lacks visible crystal faces and has no cleavage; specific gravity is about 2.6.

Identified August 19, 2026More mineral →

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At a glance

Common name: Polished chalcedony (likely carnelian or brown agate)
Scientific name: Microcrystalline quartz, SiO₂; chalcedony variety with iron-oxide coloration
Category: mineral
Identified: August 19, 2026
Method: Standard

AI Estimated Value

Approximately $5–$25 for a small common polished specimen; $30–$100+ if unusually translucent, patterned, or attractively colored.

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

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, precipitating in layers; iron oxides create the warm brown-red colors. Individual formation ages vary, commonly Mesozoic to Cenozoic.

Uses & applications

Used for cabochons, beads, carvings, and decorative objects; durable polished pieces are popular with collectors. Common material has modest commercial value.

Geological facts

The specimen appears tumbled or polished, with translucent chalcedony and possible agate-like banding or iron staining. Carnelian is the orange-red equivalent, while brown material is often marketed as brown agate or sard.

Field identification & locations

Identify by its waxy translucence, smooth conchoidal fracture, lack of cleavage, and quartz-like hardness; it should resist scratching by a steel knife. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.