Judging quality
Look for complete specimens with visible chambering and clean contrast against the matrix. Some plates are assembled from separate fossils set into cast material.
Fossil
Orthoceras
Straight-shelled cephalopods from the Devonian seas, now polished into black limestone plates that read like ink drawings.
Care
Limestone matrix is soft and scratches. Wipe with a damp cloth.
History & lore
The Erfoud quarries of Morocco have supplied fossil slabs and tables to collectors worldwide for decades.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Orthoceras
- What is Orthoceras?
- Straight-shelled cephalopods from the Devonian seas, now polished into black limestone plates that read like ink drawings.
- How hard is Orthoceras and what is it made of?
- Orthoceras is a Fossil-family mineral with the composition CaCO3. It crystallizes in the orthorhombic system and rates 3-4 on the Mohs hardness scale. It occurs in black, grey.
- Where does Orthoceras come from?
- Notable localities for Orthoceras include Morocco (Erfoud).
- How do you tell good Orthoceras from filler?
- Look for complete specimens with visible chambering and clean contrast against the matrix. Some plates are assembled from separate fossils set into cast material.
- How do you care for Orthoceras?
- Limestone matrix is soft and scratches. Wipe with a damp cloth.
See it in person
Photographs only go so far
Both rooms are open six days a week, and there is always someone happy to pull pieces out of the case so you can compare them under the light.