• Igneous rocks are classified by composition and texture.
  • Categories go from from felsic to ultramafic.
  • Texture indicates how a rock cooled.
  • Magma that cools rapidly has small or no visible crystals, while magma that cooled slowly has large crystals.
  • Use the resource below to answer the questions that follow.
  • The questions are: Is this an intrusive or an extrusive igneous rock?
  • How does the rate of magma cooling affect crystal size?
  • What is the name of the texture if extremely small crystals form?
  • Where do rocks like this form?
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