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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.
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.
Some organic material, like tree trunks, can be petrified.
The oldest fossils ever discovered are more than 3.5 billion years old.
Fossils are found all over the world and on every continent.
A paleontologist is a scientist that studies fossils.
Types of Fossils There are two main types of fossils: body fossils and trace fossils.
There are some rare places where a whole animal can be preserved.
When we think of fossils, the first things that come to mind are the bones of dinosaurs; but a fossil can be anything.