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mineral

solid object found in nature that has never been alive

hardness

a measure of how difficult it is for a mineral to be scratched

rock

a naturally formed solid made of one or more minerals

igneous rock

rock that was once melted and then cooled and hardened

sedimentary rock

rock made when materials settle into layers and get squeezed until they harden into rock

metamorphic rock

rock that has been changed by heat or pressure

humus

the part of soil made up of broken down pieces of dead plants and animals

sand

soil with grains of rock that you can see with your eyes alone

silt

soil with grains of rock that are too small to see with your eyes alone

clay

soil with very, very tiny grains of rock (holds water)

loam

soil that is a mixture of humus, sand, silt, and clay

weathering

the breaking down of rock into smaller pieces

erosion

the movement of weathered rock and soil

fossil

the hardened remains of a plant or an animal that lived long ago

extinct

describes a kind of living thing that is no longer found on Earth

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