Lesson Plan


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In this lesson, students connect igneous rock specimens to their formation in geological environments. Students will:

  • investigate specimens of basalt, granite, pumice, and obsidian.

  • differentiate between magma, lava, minerals, and glass.

  • model rates of cooling, relating the results to crystal formation in igneous rocks.

  • connect igneous rocks (granite, basalt, pumice, obsidian) to their formation within geological environments.

Essential Questions

Essential questions haven't been entered into the lesson plan.


  • Basalt: A dense, dark-colored igneous rock created by lava flow.

  • Crystal: An ordered arrangement of particles of matter in which the pattern is repeated in all directions.

  • Granite: A light-colored igneous rock with crystals that can be seen without a magnifying lens.

  • Igneous Rock: A rock formed by the solidification of molten (melted) rock.

  • Lava: Molten rock that flows out on the Earth’s surface.

  • Magma: Hot, molten rock beneath the Earth’s surface.

  • Mineral: A naturally occurring, solid crystalline substance.

  • Obsidian: A dark, shiny, volcanic glass, often used in jewelry, which fractures in a smooth, shell-like curve.

  • Physical Property: A characteristic of an object that can be observed without changing what the object is made of.

  • Pumice: An igneous rock formed when lava erupts from a volcano, trapping gases in bubbles that leave empty spaces in the rock.

  • Rock: Naturally occurring solid mixtures of minerals (and sometimes nonminerals like volcanic glass or coal).


90 minutes

Prerequisite Skills


  • an apple for display

  • igneous rock pictures (S-6-1-1_Igneous Rock Pictures.doc)

  • plastic magnifying lens per student

  • box of numbered mineral specimens (feldspar—pink and white, smoky quartz, biotite) with key, per student group

  • box of numbered igneous rock specimens (granite, basalt, obsidian, pumice) with key, per student group

Note: Granite containing pink feldspar is preferred as it will be used in Lesson 3 as well.

  • 25 large elbow macaroni pieces in a container, per student group

  • one 12-inch ruler per student group
  • one stopwatch per student group

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