3.3 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 term best describes igneous rocks?

• soft and dense

• hard and dense

• light and easily broken

• soft and smooth

How do coarse-grained igneous rocks form?

• from large rock particles cemented together

• from slowly cooling magma

• from sedimentary rocks changed under pressure

• from rapidly cooling lava

Which igneous rock is an extrusive rock?

• granite

• pegmatite

• porphyry

• rhyolite

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

• obsidian

• basalt

• perlite

• granite