sedimentary

Gray sedimentary rock, likely limestone

Likely calcite-rich limestone (primarily CaCO₃); exact identification is uncertain from the photograph.

AI-generated identification · may be incorrect

Gray-brown, dull, fine-grained and irregularly fractured, with possible small calcite grains. Limestone is typically Mohs 3, has no consistent cleavage, and commonly reacts with dilute acid; crystal structure depends on its calcite or dolomite content.

Identified October 8, 2026More sedimentary →

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At a glance

Common name: Gray sedimentary rock, likely limestone
Scientific name: Likely calcite-rich limestone (primarily CaCO₃); exact identification is uncertain from the photograph.
Category: sedimentary
Identified: October 8, 2026
Method: Standard

AI Estimated Value

About $1–$10 for an ordinary unpolished hand specimen; higher value would require distinctive fossils, provenance, or display quality.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Likely formed from accumulated carbonate mud or skeletal material that compacted and cemented on an ancient seafloor. Its geological age and depositional setting cannot be determined from appearance alone.

Uses & applications

Limestone is widely used for cement and lime, aggregate, building stone, and soil treatment; this rough piece is mainly suitable for collecting or testing.

Geological facts

Limestone can be difficult to distinguish visually from dolostone or other fine-grained rocks. A drop of dilute hydrochloric acid fizzes strongly on calcite-rich limestone.

Field identification & locations

Check for fizz with dilute acid and whether a knife can scratch it; both support limestone, though surface weathering can affect results. Limestone is common in sedimentary basins worldwide.