mineral

Botryoidal chalcedony (possibly agate/geode material)

Microcrystalline quartz, SiO₂; commonly intergrown with calcite and iron oxides

AI-generated identification · may be incorrect

White to gray, lumpy botryoidal surfaces with translucent quartz-like areas, earthy brown iron staining, and drusy sparkle; Mohs hardness about 6.5–7, vitreous to dull luster, no cleavage, and conchoidal fracture. The cavities and rounded forms suggest a silica-rich geode or replacement texture.

Identified September 10, 2026More mineral →

Explore Botryoidal chalcedony (possibly agate/geode material) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

At a glance

Common name: Botryoidal chalcedony (possibly agate/geode material)
Scientific name: Microcrystalline quartz, SiO₂; commonly intergrown with calcite and iron oxides
Category: mineral
Identified: September 10, 2026
Method: Standard

AI Estimated Value

Approximately $10–$60 for a typical hand specimen; $75–$200+ for unusually attractive, large, or locality-documented material.

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-bearing groundwater precipitates microcrystalline quartz in vesicles, cavities, or carbonate-rich rock, often later incorporating calcite and iron oxides. Its exact geological age and locality cannot be determined from the photograph.

Uses & applications

Used as a collector specimen, lapidary rough, and occasionally for polished decorative pieces; too irregular and impure for most jewelry. Commercial value is usually modest unless the specimen has exceptional translucency, drusy crystals, or a documented locality.

Geological facts

The rounded “grape-like” texture is called botryoidal and develops through repeated mineral growth. Some pale areas may be calcite rather than chalcedony, so acid and hardness tests are useful.

Field identification & locations

Common in volcanic cavities and hydrothermal veins worldwide, including Brazil, Mexico, Morocco, Uruguay, and the United States. Test with a steel file or quartz point, inspect for conchoidal fracture, and apply dilute acid only to a hidden spot to detect calcite fizzing.