mineral

Likely botryoidal chalcedony (possibly ocean jasper)

Microcrystalline quartz, SiO₂; botryoidal variety

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray, blue-gray, cream, and brown coloration with rounded botryoidal textures and a waxy to dull luster. Quartz has trigonal crystal structure but is cryptocrystalline here, with no obvious cleavage and conchoidal fracture.

Identified August 22, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, depositing concentric chalcedony layers; the specimen may be associated with volcanic rocks, potentially Miocene ocean jasper from Madagascar. Exact age and locality require testing or provenance.

Uses & applications

Used as a decorative stone, cabochon, lapidary material, and collectible; tougher pieces can be polished for jewelry or carvings.

Geological facts

Botryoidal surfaces resemble clusters of grapes and result from repeated silica deposition. The visible pattern is suggestive of ocean jasper, but the photograph cannot confirm that identification.

Field identification & locations

Field clues include glass-scratching hardness, waxy luster, curved fracture, and fine-grained texture; it should not fizz in dilute acid. Common chalcedony occurs worldwide, while ocean jasper is notably associated with Madagascar.