Rocks & Fossils
Check out our rock and fossil FAQ for smart collecting tips, information about some local rock formations, and advice about fossil eggs and meteorites.
- Rocks & Fossils
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Identification of rocks
I have no idea what these rocks are. I need help in identifying.
We can’t be 100% sure without seeing these in person, but here’s what we can say based on these photos: The large rock in the foreground of your photo of many rocks is a mica schist. The rock with the crystal-lined cavity inside it is by definition a geode. The smaller rock with reddish-brown outer layers and a milky white (maybe chalcedony) fill— second from the left in the one picture and upper right-hand corner in the other—is perhaps what we’d call a thunderegg.
Dibblee Collection Manager of Earth Science Jonathan Hoffman, Ph.D.
Nature Education Manager Sabina Thomas, Ph.D.