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There are 3 main types, or classes, of rocks in the world and in this set. They are igneous,
metamorphic, and sedimentary.
Igneous rocks are formed when magma (molten rock deep in the earth) cools and
hardens. When magma escapes from inside the earth, it is called lava.
Metamorphic rocks are formed when one type or rock changes (metamorphoses) into a new
type of rock due to extreme heat and pressure inside the earth.
Sedimentary rocks are formed when layers of material are added on top of existing rock over a
long period of time. Sedimentary rocks are usually soft and may break apart or crumble easily.
*Rock colors and features may vary.
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