fossil

Fossilized ammonite fragment

Ammonoidea; commonly Jurassic or Cretaceous ammonite, preserved mainly as calcite

AI-generated identification · may be incorrect

Fossil shell impression with coiled, chambered ornamentation and gray-brown weathered surface; original aragonite is commonly replaced by calcite or mineral infill. Hardness is typically about 3–4, with dull to locally waxy luster; exact density and cleavage depend on preservation.

Identified August 30, 2026More fossil →

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Physical properties

Formation & geological history

Ammonites were extinct marine cephalopods whose shells accumulated in seafloor sediments and fossilized through burial, compaction, and mineral replacement. Ammonites lived from the Devonian to the end-Cretaceous, about 409–66 million years ago.

Uses & applications

Used primarily for education, fossil collecting, display, and lapidary work; polished ammonites can be decorative, but this weathered specimen has modest commercial value.

Geological facts

The visible curved ridges and repeated chamber-like patterns are characteristic of a planispiral ammonite shell, though the specimen is too incomplete for reliable genus identification.

Field identification & locations

Look for a logarithmic coil, septa, and suture lines rather than random mineral banding; common sources include Morocco, Madagascar, the United Kingdom, Germany, and North America. Avoid acid testing because calcitic fossil material can etch.