mineral

Polished chalcedony with iron-oxide cap (probable carnelian/agate)

Microcrystalline quartz, SiO₂, with hematite/goethite inclusions

AI-generated identification · may be incorrect

Gray-blue to reddish-brown, waxy to glassy luster, cryptocrystalline structure, no visible cleavage, conchoidal fracture; Mohs hardness about 6.5–7 and specific gravity near 2.6. The red-brown area likely reflects iron-oxide staining or a separate jasper/carnelian zone.

Identified September 5, 2026More mineral →

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At a glance

Common name: Polished chalcedony with iron-oxide cap (probable carnelian/agate)
Scientific name: Microcrystalline quartz, SiO₂, with hematite/goethite inclusions
Category: mineral
Identified: September 5, 2026
Method: Standard

AI Estimated Value

About $3–$20 for a small ordinary tumbled piece; approximately $20–$100+ if unusually attractive, naturally patterned, or fashioned as jewelry.

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 rock, later incorporating iron oxides; commonly Cenozoic to older, depending on host rock. The smooth surface indicates tumbling or polishing.

Uses & applications

Used for cabochons, beads, carvings, decorative objects, and lapidary practice; attractive color zoning can increase jewelry and collector appeal.

Geological facts

Chalcedony is an aggregate of microscopic quartz crystals rather than a single large crystal. Red coloration commonly comes from hematite or hydrated iron oxides.

Field identification & locations

Likely chalcedony or agate, but the photograph cannot confirm the exact variety. Test for glassy conchoidal fracture and hardness, and inspect translucency; common sources include Brazil, Uruguay, India, Madagascar, and the western United States.