Igneous Rocks

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

• True
• False

___________ rock is igneous rock formed from lava that erupted onto Earth's surface. 

• extrusive
• intrusive 

Igneous rock that formed when magma hardened beneath the surface of Earth is called ___________ rock. 

• extrusive
• intrusive 

True or False. Different igneous rocks may have similar mineral compositions and yet have very different textures. 

• True
• False 

Magma that is _______ in silica content forms light-colored rocks such as granite. 

• high 
• low

Lava that is _________ in silica usually forms dark-colored rocks such as basalt. 

• high
• low

True or False. Slowly cooling lava forms fine-grained igneous rocks with small crystals or no crystals at all. 

• True 
• False

Where would molten rock cool more quickly, on Earth's surface or beneath the surface? 

• on Earth's surface
• beneath the surface 

True or False. Extrusive rocks have larger grains than intrusive rocks. 

• True
• False 

True or False. Igneous rocks are not use for tools and building materials. 

• True
• False