Though they may look like fossil plants, dendrites are incredible and inorganic formations that occur solely due to interactions between physics and geochemistry. These branching patterns are made of manganese oxides and commonly form on the surface of sandstones. As the manganese cools, it crystalizes into thin, tree-like shapes in the same process that creates snowflakes.

This specimen is a sandstone slab that has been imprinted with a manganese oxide dendrite in a branching pattern.