Igneous Rocks

People throughout history have used igneous rock for tools and building materials.

• True

• False

Basalt is used for cobblestones and in landscaping.

• True

• False

Extrusive rock forms beneath Earth’s surface.

• True

• False

Magma that is low in silica usually forms light-colored rocks, such as granite.

• True

• False

Igneous rocks are classified by their origin, texture, and mineral composition.

• True

• False

Extrusive rocks have larger grains than intrusive rocks.

• True

• False

Which terms best describe igneous rocks?

• Light and easily broken

• Soft and smooth

• Hard and dense

• Soft and dense

How do coarse-grained igneous rocks form?

• From sedimentary rocks changed under pressure

• From large rock particles cemented together

• From rapidly cooling lava

• From slowly cooling magma

Which igneous rock is mixed with soil and used for starting vegetable seeds?

• Perlite

• Granite

• Obsidian

• Basalt

Which igneous rock is an extrusive rock?

• Porphyry

• Rhyolite

• Pegmatite

• Granite