basalt contains mostly plagioclase feldspar, augite, and olivine
TRANSCRIPT
Rocks • a rock is a mixture of minerals
• minerals that are always found in a particular rock are called essential minerals
• minerals found in lesser quantities
are called accessory minerals
examples: granite contains mostly feldspar, quartz, hornblende, and mica
basalt contains mostly plagioclase feldspar, augite, and olivine
• some rocks are made of only one mineral
ex: limestone and marble contain mostly calcite
Formed from cooling & crystallizing of either:
lava • forms above ground
• rock formed from lava is called extrusive or volcanic
• most of Earth’s crust (all of sea floor) is volcanic
Igneous Rock
• fine texture:• small crystals (or even no crystals)
examples:
obsidian (volcanic glass)
pumice (volcanic glass foam; it floats in water)
scoria (sold as “lava rock”)
basalt (most common rock on Earth)
rhyolite (light colored)
andesite (medium colored)
or…
magma• like lava, but below ground
• rock is called intrusive or plutonic
• underground igneous rock structures are called plutons
coarse texture • crystals large enough to see with unaided eye
examples: granite (most common rock on continents) gabbro (like coarse grained basalt) diorite (like coarse grained andesite) pegmatite (very large crystals)