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Images of Minerals and Rocks, the Materials of the
Earth |
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Minerals |
Minerals are the naturally occurring chemical compounds that make up the crust of the earth. Although around 4,000 minerals are known, only a few dozen are at all common. Those that make up the bulk of rocks are called the rock-forming minerals. |
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Volcanic Igneous Rocks |
Igneous rocks are those that form from the cooling and solidification of molten rock. If the molten rock spills out at the Earth's surface as lava during the eruptions of volcanoes, it is termed volcanic (or extrusive) igneous rock. If crystals form, they are microscopic |
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Plutonic Igneous Rocks |
Molten rock (magma) that cools slowly deep underground develop into visible crystals and is termed plutonic (or intrusive) igneous rock. |
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Sedimentary Rocks |
When rocks of any kind are exposed at the Earth's surface, they are altered by gases, water and acids, and disintegrate and decompose into smaller fragments and new minerals. After erosion and transport and gluing (lithification) of the resulting fragments, the solid material is termed sedimentary rock. |
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Metamorphic Rocks |
When rocks are buried deep in the Earth's crust, they are subjected to intense heat and/or pressure. If they melt, they become magma. If they are changed without melting, the resulting material is termed metamorphic rock. |
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