Key Terms in Geology and Rock Types

mineral

Naturally occurring inorganic solid with a defined composition.

silicate mineral

Minerals containing silicon and oxygen as primary components.

clay

Fine-grained soil material with plasticity when wet.

ferromagnesian

Minerals rich in iron and magnesium.

rock

Solid aggregate of one or more minerals.

igneous

Rock formed from cooled molten material.

mafic

Igneous rocks rich in magnesium and iron.

felsic

Igneous rocks rich in silica and aluminum.

plutonic

Igneous rocks formed beneath Earth's surface.

volcanic

Igneous rocks formed from lava at Earth's surface.

rock cycle

Continuous process of rock transformation and recycling.

sedimentary

Rocks formed from sediment accumulation and compaction.

weathering

Breakdown of rocks due to environmental factors.

erosion

Removal and transport of surface materials by agents.

clastic

Sedimentary rocks composed of fragments from other rocks.

evaporite

Sedimentary rock formed by evaporation of water.

lithified

Process of turning sediment into solid rock.

metamorphic

Rocks altered by heat, pressure, or chemically.

foliation

Layering in metamorphic rocks due to pressure.