1. Education

Concretions, Nevada

Pictures of Sedimentary Structures

Concretions are not fossils, but form as minerals come out of solution to cement young sediments together. Learn and see more in the Concretions Gallery.
Knobby afterthoughts

From Valley of Fire State Park, Nevada

Photo (c) 2008 Andrew Alden, licensed to About.com (fair use policy)

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