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Rock Types

There are three types of rocks.  Sedimentary, Igneous, and Metamorphic.

Sedimentary rocks are made when existing rocks are weathered into sediment and that sediment is compacted and cemented to create a sedimentary rock.  Sedimentary rocks often have layers and a grainy or sandy texture.  Examples of sedimentary rocks are conglomerate, sandstone, and shale.

Igneous rocks are made when minerals are melted into magma and then cooled.  They may be made underground when magma cools; these are called intrusive.  They may also be made above ground when magma erupts to become lava and then cools; these rocks are called extrusive.  Igneous rocks may be holey, glassy or have visible crystals.  Examples of igneous rocks are basalt, obsidian, pumice, and granite.

Metamorphic rocks are made when existing rocks are buried and subjected to heat and pressure without melting.  Each metamorphic rock has a parent rock, the rock it is made of.  Metamorphic rocks may have ripples and  looked stretched, crystallized or shiny.  Examples of metamorphic rocks are gneiss, marble, slate, and schist.

Rock Types and Rock Cycle Interactive Activity