rock

rock, aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic.

Sections in this article:

• Introduction
• Metamorphic Rocks
• Sedimentary Rocks
• Igneous Rocks
• Bibliography

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