mineral

Botryoidal chalcedony (possibly calcite)

Microcrystalline quartz, SiO₂; visual identification is uncertain and carbonate minerals are also possible

AI-generated identification · may be incorrect

Cream to honey-colored, waxy luster, with rounded grape-like bumps; chalcedony has Mohs hardness 6.5–7 and no cleavage, while calcite is softer (Mohs 3) and fizzes in dilute acid.

Identified October 7, 2026More mineral →

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Physical properties

Cream to honey-colored, waxy luster, with rounded grape-like bumps; chalcedony has Mohs hardness 6.5–7 and no cleavage, while calcite is softer (Mohs 3) and fizzes in dilute acid.

Formation & geological history

Botryoidal surfaces form as silica- or carbonate-rich fluids deposit successive layers in cavities and fractures. This texture occurs in rocks of many ages and settings.

Uses & applications

Attractive pieces are collected or used in lapidary work; chalcedony may be cut or polished for ornaments and jewelry.

Geological facts

“Botryoidal” describes the clustered, rounded form, from a word meaning grape-like; appearance alone cannot reliably distinguish chalcedony from calcite.

Field identification & locations

Check hardness and, if appropriate, a tiny inconspicuous spot with dilute acid: quartz resists scratching by steel and does not fizz; calcite scratches readily and fizzes. Botryoidal chalcedony occurs worldwide in volcanic cavities and veins.