sedimentary

Concrete-like limestone or cemented carbonate rock

Likely limestone (calcium carbonate, CaCO₃); exact identification is uncertain from the image

AI-generated identification · may be incorrect

Light gray, massive, fine- to medium-grained, and dull to weakly crystalline; likely Mohs hardness 3, with poor visible cleavage and specific gravity near 2.6–2.7. The rough surface and angular shape may indicate a quarried or processed building stone.

Identified August 29, 2026More sedimentary →

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At a glance

Common name: Concrete-like limestone or cemented carbonate rock
Scientific name: Likely limestone (calcium carbonate, CaCO₃); exact identification is uncertain from the image
Category: sedimentary
Identified: August 29, 2026
Method: Standard

AI Estimated Value

$5–$30 for an ordinary fragment or building-stone specimen; architectural blocks are valued mainly by size and local construction pricing.

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

If natural limestone, it formed from compacted marine carbonate sediments, commonly during Paleozoic–Mesozoic seas; the apparent cut block may be human-shaped. It could also be cast concrete, which is not a geological specimen, but the image alone cannot confirm this.

Uses & applications

Limestone is used for aggregate, masonry, cement, lime, and architectural stone; polished varieties are used decoratively. Common gray building limestone generally has modest collector value.

Geological facts

Limestone effervesces strongly with dilute hydrochloric acid or household vinegar if fresh and uncoated; concrete may also react weakly because of exposed aggregate or carbonate filler.

Field identification & locations

Common worldwide, especially in former shallow-marine basins. Test a concealed spot for fizz, inspect for sand/gravel aggregate, and avoid assuming it is natural stone without a close view.