sedimentary

Fossil-bearing limestone or calcareous mudstone pebble

Micritic limestone, primarily calcite (CaCO₃), with possible fossil or iron-oxide vein features

AI-generated identification · may be incorrect

Cream to tan, dull-to-waxy surface with dark brown branching cracks or fossil traces; calcite-rich material has Mohs hardness 3, weak cleavage, and specific gravity about 2.7. It should effervesce strongly with dilute hydrochloric acid or vinegar if sufficiently fresh.

Identified August 28, 2026More sedimentary →

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At a glance

Common name: Fossil-bearing limestone or calcareous mudstone pebble
Scientific name: Micritic limestone, primarily calcite (CaCO₃), with possible fossil or iron-oxide vein features
Category: sedimentary
Identified: August 28, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 as a common pebble; approximately $10–$40 if the markings are confirmed as an attractive or identifiable fossil.

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 compacted carbonate mud and/or skeletal debris in a marine sedimentary environment, later lithified and rounded by weathering or stream transport. Its exact geological age cannot be determined from the image alone.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and occasionally as a decorative or fossil-collecting specimen. This example has modest lapidary value unless the dark markings prove to be a distinctive fossil.

Geological facts

The dark branching feature may be a fossil burrow, mineral-filled fracture, manganese-oxide dendrite, or weathered crack rather than a true plant fossil.

Field identification & locations

Common in limestone terrains and river or beach gravels; inspect freshly broken surfaces and test acid reaction, streak, and hardness. Avoid acid testing on valuable specimens, and use a hand lens to distinguish fossil structures from surface staining.