The three classes of rocks are sedimentary, metamorphic and igneous. The most significant differences found among these the three types have to do with how the rock is formed. More »

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The three major types of rocks are igneous, sedimentary and metamorphic. Formed deep inside the Earth, igneous rocks form when a melted rock cools and solidifies. This liquid rock is magma, and the rate of cooling determ... More »

All rocks fall into the three main categories of igneous, metamorphic or sedimentary. These rocks vary widely in physical appearance and location and their formation patterns differ, as well: igneous rocks form cooling m... More »

Rocks have three main types or classes, which are sedimentary rocks such as limestone, igneous rocks such as obsidian, and metamorphic rocks such as marble. Sedimentary rocks are formed when layers of material accumulate... More »

The three major types of rocks are igneous, sedimentary and metamorphic. Formed deep inside the Earth, igneous rocks form when a melted rock cools and solidifies. This liquid rock is magma, and the rate of cooling determ... More »

Four types of pyroclastic materials include ash, lapilli, lava blocks and floating rocks. Pyroclastic materials are ejected during a volcano. Ash is the most common type of pyroclastic material. More »

All rocks fall into the three main categories of igneous, metamorphic or sedimentary. These rocks vary widely in physical appearance and location and their formation patterns differ, as well: igneous rocks form cooling m... More »