mineral

Calcite rosette (possibly fossilized shell fragment)

Calcite, CaCO₃; crystal habit appears botryoidal/rosette-like

AI-generated identification · may be incorrect

Soft (Mohs 3), white to cream, pearly–vitreous luster, commonly rhombohedral cleavage, and relatively low density (specific gravity ~2.71). It should fizz vigorously with dilute hydrochloric acid or strong vinegar if exposed fresh.

Identified September 6, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed by precipitation from carbonate-rich groundwater or hydrothermal fluids, potentially as a layered rosette; exact age cannot be determined from the image. Similar calcite occurs in limestone cavities, caves, veins, and sedimentary deposits.

Uses & applications

Used for cement, lime, aggregate, optical calcite, and mineral collecting; attractive rosettes are decorative specimens rather than gemstones.

Geological facts

The rounded, layered form may also represent a calcitic fossil or concretion, and a photograph alone cannot distinguish these confidently.

Field identification & locations

Common in limestone regions, Mexico, the United States, Morocco, and China. Check acid reaction, scratchability with a copper coin or steel blade, and cleavage; avoid scratching the specimen unnecessarily.