mineral

Botryoidal chalcedony (possibly agate/geode material)

Microcrystalline quartz, SiO₂; commonly chalcedony with quartz-lined cavities and iron-oxide staining

AI-generated identification · may be incorrect

White, cream, tan, and brown rounded botryoidal surfaces with waxy to dull luster and small sparkling quartz druses. Hardness about 6.5–7 Mohs, no cleavage, conchoidal fracture, cryptocrystalline structure; specific gravity about 2.58–2.64.

Identified August 11, 2026More mineral →

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At a glance

Common name: Botryoidal chalcedony (possibly agate/geode material)
Scientific name: Microcrystalline quartz, SiO₂; commonly chalcedony with quartz-lined cavities and iron-oxide staining
Category: mineral
Identified: August 11, 2026
Method: Standard

AI Estimated Value

About $10–$40 for a common hand specimen; $50–$200+ for large, vividly colored, well-crystallized collector pieces.

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 or vesicles in volcanic rock, depositing concentric chalcedony layers and later quartz crystals; iron oxides create the brown coloration. Formation is generally Cenozoic to older, depending on the host rock.

Uses & applications

Used as a lapidary, carving, ornamental, and display material; attractive pieces may be polished or cut into cabochons. Ordinary specimens have modest commercial value.

Geological facts

The rounded “grape-like” texture is called botryoidal growth and develops from repeated silica precipitation around nucleation points.

Field identification & locations

Identify by its very hard, glassy fracture, inability to scratch with a steel knife, and waxy chalcedony texture; acid should not fizz. Similar material occurs in volcanic regions worldwide, including Brazil, Mexico, Uruguay, India, and the western United States.