mineral

Botryoidal chalcedony (likely white quartz/chalcedony)

Microcrystalline quartz, SiO₂; possibly partly altered carbonate or opaline silica

AI-generated identification · may be incorrect

White to cream, waxy-to-dull luster with rounded botryoidal (“grape-like”) growths and a darker gray-brown matrix. Quartz hardness is about 6.5–7 Mohs, lacks cleavage, has cryptocrystalline structure, and specific gravity near 2.6; the exact specimen may include softer porous material.

Identified August 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater precipitates in cavities, fractures, or vesicles, building concentric botryoidal crusts. Such deposits commonly formed during low-temperature hydrothermal or weathering processes, with age varying by locality.

Uses & applications

Used as a decorative and lapidary stone, ornamental carving material, and collector specimen; polishability depends on whether the surface is solid chalcedony or porous alteration material.

Geological facts

Botryoidal chalcedony is often called “grape agate” when translucent and vividly colored, though this specimen appears mostly opaque and white.

Field identification & locations

Test hardness on an inconspicuous spot: genuine chalcedony scratches glass, while calcite or clay-rich material does not. Common occurrences include volcanic cavities and silica-rich weathering zones worldwide; locality confirmation requires testing or provenance.