Rock Identifier
Orthoceras Fossil (Orthoceras regulare (Extinct Cephalopod)) — fossil
fossil

Orthoceras Fossil

Orthoceras regulare (Extinct Cephalopod)

Hardness: 3-4 (calcite matrix); Color: Black or dark grey with white/light grey fossil inclusions; Luster: Dull to sub-vitreous (when polished); Structure: Straight-shelled nautiloid with visible chambers and siphuncle.

Hardness
3-4 (calcite matrix)
Color
Black or dark grey with white/light grey fossil inclusions
Luster
Dull to sub-vitreous (when polished)
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Physical properties

Hardness: 3-4 (calcite matrix); Color: Black or dark grey with white/light grey fossil inclusions; Luster: Dull to sub-vitreous (when polished); Structure: Straight-shelled nautiloid with visible chambers and siphuncle.

Formation & geological history

Formed in marine environments during the Ordovician period (~488 to 443 million years ago). They are frequently found in limestone beds where the soft tissues decayed and were replaced by minerals like calcite.

Uses & applications

Primarily used for decorative purposes, educational specimens, jewelry (pendants and beads), and as a popular entry-level collector's item.

Geological facts

Orthoceras lived underwater and could grow from a few centimeters to over 14 feet long. They are ancestors of the modern squid and octopus. The name means 'straight horn'.

Field identification & locations

Mostly found in the Anti-Atlas Mountains of Morocco. Field identification involves looking for white, bullet-shaped or conical outlines against a dark, fine-grained sedimentary matrix.

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