Igneous Rocks

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

• true
• false

Which term best describes igneous rocks?

• light and easily broken
• soft and smooth
• hard and dense
• soft and dense

Basalt is used for cobblestones and in landscaping.

• true
• false

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

Extrusive rock forms beneath Earth's surface.

• true
• false

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

• perlite
• granite
• obsidian
• basalt

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

• true
• false

Which igneous rock is an extrusive rock?

• porphyry
• rhyolite
• pegmatite
• granite

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

• true
• false

Extrusive rocks have larger grains than intrusive rocks.

• true
• false