fossil

Ammonite fossil in limestone/marl matrix

Ammonoidea (likely Jurassic or Cretaceous ammonite); matrix primarily calcite-rich limestone or marl

AI-generated identification · may be incorrect

Fossilized coiled shell with ribbing and visible chamber divisions; shell material is commonly recrystallized calcite. Mohs hardness about 3–4, dull to pearly luster, typically gray-brown; matrix is softer, earthy, and uneven.

Identified September 9, 2026More fossil →

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At a glance

Common name: Ammonite fossil in limestone/marl matrix
Scientific name: Ammonoidea (likely Jurassic or Cretaceous ammonite); matrix primarily calcite-rich limestone or marl
Category: fossil
Identified: September 9, 2026
Method: Standard

AI Estimated Value

Approximately $15–$100 for a common matrix specimen; $100–$500+ if unusually large, well-prepared, or from a desirable locality.

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

Ammonites were extinct marine cephalopods whose shells were buried in seafloor sediment and mineral-replaced or infilled during diagenesis. Most collectible examples date from roughly 410–66 million years ago, with exact age requiring locality or diagnostic morphology.

Uses & applications

Primarily used for education, display, and collecting; polished ammonites may be decorative. Commercial value depends heavily on species, preservation, size, preparation, and locality.

Geological facts

The spiral is a logarithmic growth pattern, and internal chambers were connected by a siphuncle that helped regulate buoyancy. The specimen appears partly prepared, with the fossil still embedded in host rock.

Field identification & locations

Identify by the tightly coiled, ribbed shell and chambered structure; confirm with an acid test on exposed matrix, not the fossil. Common sources include Morocco, Madagascar, the United Kingdom, Germany, and Alberta, Canada.