The Rock Cycle Explained: How Three Main Rock Types Form
The rock cycle explains how rocks change over time. There are three main rock groups: igneous, sedimentary and metamorphic.
Igneous rocks: cooling from melted rock
Magma is melted rock below the surface. When melted rock cools and becomes solid, it forms igneous rock.
Sedimentary rocks: pieces become rock
Weathering breaks rocks into smaller pieces. Water, wind or ice can move these pieces. Sediment builds up in layers. Compaction and cementation can turn it into sedimentary rock.
Metamorphic rocks: change without melting
Heat and pressure can change a solid rock into metamorphic rock. Melting is a different process. If rock melts, it becomes magma and may later form igneous rock.
Does every rock follow the same path?
No. The rock cycle is a model with many possible paths. A rock can be weathered, buried, changed or melted. It does not have to pass through all three groups in a fixed order.
A simple observation activity
Look at a rock without breaking it. Write down its color, visible grains and any layers. Photograph it beside a ruler. These notes are a starting point, not a final identification. A mineral such as andalusite can give useful geological clues, but one crystal alone does not tell the whole story.
Related guides on Gemology Hub
- Albite Mineral: Properties, Identification and Collector Care
- Andalusite Mineral: Properties, Crystal Shape and Formation
- What Is a Pallasite Meteorite? Olivine Crystals and Space Metal
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