In general, extrusive igneous rocks are composed of mineral grains visible to the unaided eye, whereas mineral grains in intrusive igneous rocks are too small to be seen without magnification.

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Extrusive igneous rocks generally cool quickly on the Earth's surface, leading to the formation of small crystals that are often too fine to be seen without magnification. Intrusive igneous rocks cool slowly beneath the Earth's surface, allowing for the growth of larger crystals that are typically visible to the unaided eye.

In General, Extrusive Igneous Rocks Are Composed of Mineral Grains