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Igneous Rock
Key Concepts
• What characteristics are used to classify
igneous rock?
• How are igneous rocks used?
Key Terms
• Extrusive rock
• Intrusive rock
• Silica
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• Classifying Igneous Rocks
– Igneous rocks are classified according to their
origin, texture, and mineral composition
– Extrusive rock: is igneous rock formed from lava
that erupted onto Earth’s surface
– Intrusive rock: igneous rock that formed when
magma hardened beneath Earth’s surface
– Silica: a material formed from oxygen and silicon
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• Uses of Igneous Rocks
– People throughout history have used igneous rock
for tools and building materials