Metamorphic Rocks

- we're sometimes igneous or sedimentary rocks, there is just an effect on temperature on pressure on these rocks that they turned into metamorphic rocks.

Sedimentary Rocks

- are formed by sediments, and also when weathering and erosion occurs that breaks the rocks. 

Igneous Rocks

- are formed in volcanoes, when lava and magma are cooling.

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Igneous rocks are formed from solidification of lava deposit
Examples are granite, basalt, obsidian

Sedimentary rocks are formed by the sedimentation and deposition of materials in the Earth's surface and the water. 
Examples are shale, conglomerate, sandstone and limestone

Metamorphic rocks are formed as a result from a pre-existing rock (may be either an igneous or sedimentary). The original rock is subjected to such a high heat and temperature which affects the composition, silica content, and texture of the rock
Examples are quartz, marble(from sandstone), gneiss