Molds and Casts A mold is a hollow space left in a rock by an object that has dissolved in it If this mold fills in with mud or minerals, the filling can harden, resulting in a cast
Formation An organism dies and lands in soft sediment The sediment becomes rock over time Water seeps into the rock, decaying/dissolving the organism, leaving a mold Minerals fill the mold and create a cast of the organism
Conditions Water – decays the organism Sedimentary rock – layers over the top of the dead organism. Other types of rock don’t layer and couldn’t form a mold