mineral

Botryoidal chalcedony/geode fragment

Microcrystalline quartz (SiO₂), likely limonite/goethite-stained chalcedony with druzy quartz

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; cream to brown outer rind with a cavity lined by golden-brown, botryoidal to druzy crystals. Waxy to vitreous luster, cryptocrystalline quartz structure, no obvious cleavage, and conchoidal fracture; the rusty color likely comes from iron oxides.

Identified August 21, 2026More mineral →

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At a glance

Common name: Botryoidal chalcedony/geode fragment
Scientific name: Microcrystalline quartz (SiO₂), likely limonite/goethite-stained chalcedony with druzy quartz
Category: mineral
Identified: August 21, 2026
Method: Standard

AI Estimated Value

About $5–$25 for a small ordinary fragment; $30–$150+ if the cavity has unusually vivid color, well-formed crystals, or a desirable 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 or vesicles in volcanic rock, depositing chalcedony and later quartz crystals; iron-bearing fluids create the brown-gold staining. The exact geological age and locality cannot be determined from the photograph.

Uses & applications

Used as a decorative specimen, lapidary material, and occasionally in cabochons or polished slices; attractive examples are mainly valued by collectors.

Geological facts

The rounded “grape-like” texture is called botryoidal. A cavity lined with tiny quartz crystals is commonly marketed as a geode or quartz-lined nodule.

Field identification & locations

Look for a lightweight-to-moderate, silica-hard rind that scratches glass, conchoidal fracture, and crystal sparkle inside cavities; acid should not fizz. Common sources include volcanic terrains in Brazil, Uruguay, Mexico, the western United States, and Madagascar.