fossil
Orthoceras Fossil in Limestone
Orthoceras regulare (Class Cephalopoda)
Hardness: 3-4 (calcite matrix), Color: Dark grey to black matrix with white or cream fossil, Luster: Dull to sub-vitreous, Structure: Internal molds showing chambers (septa) and siphuncle.
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Physical properties
Hardness: 3-4 (calcite matrix), Color: Dark grey to black matrix with white or cream fossil, Luster: Dull to sub-vitreous, Structure: Internal molds showing chambers (septa) and siphuncle.
Formation & geological history
Formed in marine environments during the Ordovician period (~485 to 443 million years ago) when these straight-shelled cephalopods died and were buried in limey sediment.
Uses & applications
Commonly used for ornamental pieces, paperweights, jewelry, and educational collections due to its accessibility and striking contrast.
Geological facts
Orthoceras were ancestors to the modern squid and lived inside long, conical shells. They used gas-filled chambers to control leur buoyancy in the Paleozoic oceans.
Field identification & locations
Identify by looking for the distinctive internal 'ladder' structure of the shell chambers surrounded by a dark sedimentary matrix. Commonly found in the Anti-Atlas Mountains of Morocco.
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