mineral
Botryoidal calcite (likely calcite concretion)
Calcite, calcium carbonate (CaCO₃)
AI-generated identification · may be incorrectCreamy white to honey-colored, dull-to-pearly luster, rounded botryoidal masses, and prominent rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. It may fizz vigorously with dilute hydrochloric acid or vinegar, though vinegar is slower.
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Physical properties
Creamy white to honey-colored, dull-to-pearly luster, rounded botryoidal masses, and prominent rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. It may fizz vigorously with dilute hydrochloric acid or vinegar, though vinegar is slower.
Formation & geological history
Forms when calcium-carbonate-rich groundwater precipitates in cavities, fractures, or sediment, commonly as botryoidal crusts and concretions. Its exact age cannot be determined from the image; deposits range from modern to ancient sedimentary formations.
Uses & applications
Used for cement, lime, agricultural soil treatment, construction stone, and ornamental specimens; attractive translucent pieces may be collected but are generally not jewelry-grade.
Geological facts
The rounded “grape-like” texture is botryoidal growth, produced by successive mineral coatings rather than biological structures. Calcite is the principal mineral in limestone and marble.
Field identification & locations
Identify by its soft hardness, rhombohedral cleavage, pale color, and acid reaction; common worldwide, especially in limestone regions, caves, hydrothermal veins, and sedimentary cavities. Estimated value: $5–$30 for a common hand specimen, potentially $50–$150 if unusually attractive or locality-documented.
