Intrusive rocks

  • Exhibition Text

    • Magma is molten rock. As the mantle or crust melts, magma separates from the solid rock, rises through cracks, and collects to form chambers of varying sizes. Frequently, it reaches the surface to erupt as lava from volcanoes. But many large bodies of magma never get that far. Instead, they solidify in the crust to form intrusive rocks. There is an enormous variety of these rocks, and the characteristics of each kind are determined primarily by the composition of the magma and how rapidly it cools and crystallizes.

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  • For Educators

    • Topic: Earth Science

      Subtopic: Volcanoes

      Keywords: Intrusions (Geology), Volcanoes, Magmas, Lava, Volcanism

      Audience: General

In This Section

Anorthosite

Anorthosite

This is an anorthosite, composed almost entirely of plagioclase (white).

Harzburgite

Harzburgite

This harzburgite is one of the lowermost layers of the Stillwater Complex. 

Norite

Norite

This norite is composed of plagioclase (labradorite, white) and orthopyroxene (bronzite, brown). 

Zoned Labradorite

Zoned Labradorite

This giant labradorite crystal exemplifies the texture that results when anorthosite rocks cool very slowly.