mineral

Tumbled amber-brown chalcedony (probable carnelian/ag ate)

Microcrystalline quartz, SiO₂; likely iron-stained chalcedony (carnelian)

AI-generated identification · may be incorrect

Translucent honey-brown to gray, waxy luster, curved surfaces, and no visible cleavage; quartz hardness is about 7 Mohs and specific gravity about 2.6. The rounded shape appears tumbled or naturally waterworn, and the gray piece may be related chalcedony.

Identified August 27, 2026More mineral →

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At a glance

Common name: Tumbled amber-brown chalcedony (probable carnelian/ag ate)
Scientific name: Microcrystalline quartz, SiO₂; likely iron-stained chalcedony (carnelian)
Category: mineral
Identified: August 27, 2026
Method: Standard

AI Estimated Value

About $2–$15 for common tumbled pieces; $20–$100+ for attractive, highly translucent, patterned, or provenance-specific specimens.

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

Chalcedony forms when silica-rich groundwater fills cavities and fractures, later becoming microcrystalline quartz; iron oxides create orange-brown coloration. Its precise geological age and locality cannot be determined from the photograph.

Uses & applications

Used for beads, cabochons, carvings, ornamental objects, and lapidary collections; chalcedony is also used decoratively in architecture. Common material generally has modest value unless color, translucency, pattern, or provenance is exceptional.

Geological facts

Carnelian is the orange-red variety of chalcedony, while paler brown material is often marketed as sard or brown chalcedony. Heat treatment can intensify its red-orange color.

Field identification & locations

Commonly found in volcanic cavities, silica-rich veins, and alluvial gravels worldwide, especially Brazil, India, Madagascar, Uruguay, and the United States. Field tests include hardness sufficient to scratch glass and lack of reaction to dilute acid; confirm with a gemological test because appearance alone is inconclusive.