mineral

Tumbled brown chalcedony (likely carnelian/colored agate)

Microcrystalline quartz, SiO₂ (chalcedony; iron-bearing varieties are carnelian or brown jasper)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; reddish-brown to chocolate-brown, waxy-to-glassy luster, opaque to translucent, with no visible cleavage and a smoothly tumbled surface. The uniform appearance and lighting prevent confident separation of carnelian, jasper, or dyed chalcedony.

Identified August 25, 2026More mineral →

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At a glance

Common name: Tumbled brown chalcedony (likely carnelian/colored agate)
Scientific name: Microcrystalline quartz, SiO₂ (chalcedony; iron-bearing varieties are carnelian or brown jasper)
Category: mineral
Identified: August 25, 2026
Method: Standard

AI Estimated Value

About $2–$15 for a common tumbled stone; $20–$75 for unusually large, translucent, or attractive material.

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, precipitating cryptocrystalline quartz; iron oxides create the brown-red color. Chalcedony occurs from many geological ages and settings, commonly volcanic cavities and sedimentary veins.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and inexpensive collectible specimens; occasionally used as decorative stone. Typical value is modest unless color, translucency, or pattern is exceptional.

Geological facts

Chalcedony is composed of interlocking microscopic quartz fibers rather than large crystals. Tumbled specimens are commonly polished in commercial lapidary equipment.

Field identification & locations

Look for a waxy luster, conchoidal fracture, quartz-like hardness, and lack of cleavage; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, India, Madagascar, and the United States.