Download Igneous Rocks - Frost Middle School

 Most
rock melts around 750 C – 1250 C
 Temperatures in the mantle are at least
this high
 When molten rock hardens it forms
Igneous Rock
 Made
from Magma
• Inside the Earth’s crust
 Due
to high temperatures
• Cools slowly
• Large Crystal size
 Granite
• Most common
• Continental
• Used in countertops, paving stones, floor tiles,
ext
• Found at the surface – Mt. Rushmore, Stone Mt.
• Made up mostly of Feldspar (pink), Quartz or
Muscovite (clear or smoky gray), Biotite or
Hornblende (Black)
 Diorite
• Coarse-grained
• Usually continental
• Contains Feldspar, pyroxene, hornblende and
sometimes quartz
 Gabbro
• Usually black or dark green
• Most abundant rock deep in oceanic crust
• Usually contains
 Feldspar
 Clinopyroxene
• Very little quartz (unlike most other igneous
rocks)
 Formed
on the surface
 Formed when lava cools
 Due to cooler temperatures
• Cools quickly so small crystal structure
 Basalt
• Dark-colored
• Fine-grained
• Made mostly of plagioclase and pyroxene
minerals
• Makes up most of the ocean floor
 Pumice
• Usally Light-colored
• Vesicular
• Gas trapped in
 Rhyolite
• Light-colored
• Fine-grained
• Usually continental
• Typically made of
 Quartz
 Feldspar
 Obsidian
• Has no crystals – Cools to quickly
• Usually black in color
• Forms
 Along the edges of a lava flow
 Where lava contacts water
 When lava cools while airborn