Fossils most commonly form in which rock type?

• A. Igneous rock
• B. Metamorphic rock
• C. Sedimentary rock
• D. Glassy rock

Answer: (C)

Fossil preservation happens best when remains are buried and gradually turned into rock without being melted or blasted apart. Sedimentary rocks form from particles that settle out of water or air and accumulate in layers. When organisms die, their shells, bones, or impressions can be buried by this sediment. Over time, the layers are compacted and cemented into solid rock, locking in the fossil and often preserving fine details of its structure. This low-heat, low-pressure setting is ideal for preserving organic material.

Igneous rocks come from molten material that cools into solid rock, which involves high heat that destroys organic matter. Metamorphic rocks form under intense heat and pressure that alter or erase fossils. Glassy rocks arise from rapid cooling of lava or volcanic glass, a process that also destroys fossils rather than preserves them.

So the rock type most commonly associated with fossils is sedimentary rock.