mineral

Botryoidal chalcedony (likely purple quartz/chalcedony geode)

Chalcedony, microcrystalline SiO₂; purple coloration may indicate amethystine quartz or iron/manganese impurities

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; pale lavender to gray-purple, translucent, with waxy to vitreous luster and botryoidal, microcrystalline texture. No obvious cleavage; conchoidal fracture; density about 2.6 g/cm³.

Identified August 19, 2026More mineral →

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At a glance

Common name: Botryoidal chalcedony (likely purple quartz/chalcedony geode)
Scientific name: Chalcedony, microcrystalline SiO₂; purple coloration may indicate amethystine quartz or iron/manganese impurities
Category: mineral
Identified: August 19, 2026
Method: Standard

AI Estimated Value

About $5–$25 as a common rough specimen; $30–$100+ if strongly colored, crystalline, or from a documented locality.

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 vesicles in volcanic rock, depositing layered chalcedony and quartz. Such material commonly formed during Cenozoic volcanic activity, though exact age and locality cannot be determined from the image.

Uses & applications

Used as a lapidary material for cabochons, carvings, polished specimens, and small geodes; attractive purple pieces may be sold as amethystine chalcedony.

Geological facts

The rounded “grape-like” surface is called botryoidal texture and develops through successive silica growth. The apparent cavity may contain drusy quartz crystals or weathered matrix.

Field identification & locations

Look for translucent edges, waxy luster, conchoidal fracture, and hardness sufficient to scratch glass; it should not fizz in dilute acid. Common sources include Brazil, Uruguay, Mexico, Namibia, and the western United States.