fossil
Orthoceras fossil
Orthoceras regulare (Cephalopoda, Orthocerida)
Hardness: 3-4 (calcite-based); Color: white to light gray chambers set in a black limestone matrix; Luster: polished/vitreous; Structure: straight, conical shell with internal chambers (septa).
- Hardness
- 3-4 (calcite-based)
- Color
- white to light gray chambers set in a black limestone matrix
- Luster
- polished/vitreous
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Physical properties
Hardness: 3-4 (calcite-based); Color: white to light gray chambers set in a black limestone matrix; Luster: polished/vitreous; Structure: straight, conical shell with internal chambers (septa).
Formation & geological history
Formed during the Ordovician period (roughly 485 million to 443 million years ago). These are the remains of prehistoric cephalopods that lived in shallow seas and were preserved in seafloor sediment that turned to limestone.
Uses & applications
Primarily used for decorative purposes, educational specimens, jewelry (cabs and pendants), and as popular collector items for beginning paleontologists.
Geological facts
The name means 'straight horn,' referring to its long, conical shell. They are ancestors to the modern squid and octopus, but inhabited a hard external shell instead of an internal mantle.
Field identification & locations
Most commonly identified by the visible internal chambers and siphuncle running through the center of the cone. They are found in massive quantities in the Erfoud region of Morocco, often polished to highlight the contrast between the fossil and matrix.
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