Extremely rapid cooling of lava in which no crystals form

Igneous rock that forms from magma that cools slowly within Earth’s crust is likely to have larger crystals and a coarse-grained texture.

Igneous rock that forms from lava that cools quickly on Earth’s surface is known as extrusive igneous rock. Another word for extrusive is volcanic.

Because the sample of igneous rock formed on Earth’s surface, it is extrusive. Because it’s composed of mostly light-colored minerals, it is likely felsic.

Because the sample of igneous rock formed within Earth’s crust, it is intrusive. Because it contains a very high concentration of dark-colored, high-density minerals, it is likely ultramafic.

The fact that gabbro is an igneous rock suggests that it was formed from the cooling and crystallization of magma. The fact that it is intrusive means that it formed within Earth’s crust. The fact that it’s mafic suggests that it contains a high concentration of dark-colored, high-density minerals.

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