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1.  What is a fossil? Fossils are the remains of ancient animals and plants, the traces or impressions of living things from past geologic ages, or the traces of their activities
2.  How are fossils of hard mineral parts (like teeth and bone formed?
  • Some animals were quickly buried after their death (by sinking in mud, being buried in a sand storm, etc.).
  • Over time, more and more sediment covered the remains.
  • The parts of the animals that didn't rot (usually the harder parts likes bones and teeth) were encased in the newly-formed sediment.
  • In the right circumstances (no scavengers, quick burial, not much weathering), parts of the animal turned into fossils over time.
  • After a long time, the chemicals in the buried animals' bodies underwent a series of changes. As the bone slowly decayed, water infused with minerals seeped into the bone and replaced the chemicals in the bone with rock-like minerals. The process of fossilization involves the dissolving and replacement of the original minerals in the object with other minerals (and/or permineralization, the filling up of spaces in fossils with minerals, and/or recrystallization in which a mineral crystal changes its form).
  • This process results in a heavy, rock-like copy of the original object - a fossil. The fossil has the same shape as the original object, but is chemically more like a rock! Some of the original hydroxy-apatite (a major bone consitiuent) remains, although it is saturated with silica (rock).
3.  Where are most fossils found? Most fossils are found in sedimentary rocks - rocks which were created when shells or small loose bits of rock are laid down in layers. Examples of sedimentary rocks are limestone, sandstone, clay and chalk.