sedimentary

Fossiliferous limestone, likely stromatolitic or bioclastic limestone

Calcite-rich carbonate rock; predominantly CaCO₃ (calcite), with possible siliciclastic impurities and fossil structures

AI-generated identification · may be incorrect

Usually Mohs hardness 3, gray-tan to brown, earthy to dull luster, fine- to medium-grained, and commonly massive with irregular fracture; weak acid effervescence is diagnostic. The swirling bands appear to be fossil or laminated microbial structures, though the photograph alone cannot confirm a specific fossil.

Identified September 6, 2026More sedimentary →

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At a glance

Common name: Fossiliferous limestone, likely stromatolitic or bioclastic limestone
Scientific name: Calcite-rich carbonate rock; predominantly CaCO₃ (calcite), with possible siliciclastic impurities and fossil structures
Category: sedimentary
Identified: September 6, 2026
Method: Standard

AI Estimated Value

$5-$30 as a typical loose specimen; approximately $30-$150 if unusually attractive, large, or clearly fossiliferous.

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

Formed from accumulated marine carbonate mud, shells, or microbial mats that lithified into limestone, likely during a Paleozoic–Mesozoic marine episode; exact age requires locality and laboratory study. Weathering produced the rusty-brown iron staining.

Uses & applications

Used for aggregate, cement, lime, building stone, and landscaping; attractive fossiliferous pieces are collected as display specimens. Typically has little gem value unless polished and unusually fossil-rich.

Geological facts

Limestone can preserve reefs, shells, burrows, and stromatolites, recording ancient shallow seas. Vinegar or dilute hydrochloric acid should fizz on a fresh surface if calcite-rich.

Field identification & locations

Look for visible fossil fragments, bedding, and strong acid reaction; calcite limestone is softer than quartz and can be scratched with a steel knife. Common in former marine sedimentary basins worldwide.