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A cast fossil is like a mold fossil, but in the case of a cast fossil the mold has been filled with minerals.Imprint fossils are made when organic - or living - material is pressed into sediment, but does not decay like with a cast or mold, and the organic material leaves an impression in the formed rock.So long as the temperature remains below freezing, the animal stays frozen, sort of like a natural freezer.
For most fossils there are three basic things that are needed: sediment, pressure, and time.The two fossil categories can be broken down further.A cast fossil is a fossil made when an organism that is buried in sediment decays and leave behind a mold, or hollow impression in its shape.Some organic material, like tree trunks, can be petrified.Petrification happens when the organic material is slowly replaced by minerals. Making a fossil is tricky and the conditions have to be just right.
Fossils are found all over the world and on every continent.