Substances composed of minerals.
Rocks are made from many
minerals, so we CANNOT test properties!
Instead, rocks are defined by HOW they form (Environment
ofFormation).
Let’s start with Igneous Rocks…
Igneous Rocks
Form from solidified lava or
magma.
The flowchart below illustrates the change fromlava to the extrusive rock basalt.
The solidification of the melted rock occurred
(1) slowly, underground
(2) slowly, above ground
(3) rapidly, underground
(4) rapidly, above ground
Intrusive - Cools slowly underground Coarse (big) Crystals
Extrusive – Cools quickly above ground Fine (small) or Glassy (no
crystals). Sometimes Vesicular (“catches
gas”)
The flowchart below illustrates the change frommelted rock to basalt.
The solidification of the melted rock occurred
(1) slowly, resulting in fine-grained minerals
(2) slowly, resulting in coarse-grained minerals
(3) rapidly, resulting in fine-grained minerals
(4) rapidly, resulting in coarse-grained minerals
In addition to ash, solid rock formed on Mt. Hekla from the lava extruded during an eruption. This rock is most likely
(1) light-colored metamorphic (2) fine-grained igneous(3) dark-colored metamorphic (4) coarse-grained igneous
Mt. Hekla
MAFICFELSIC
Which igneous rock is probably best described as being non-vesicular and mafic?
(1) andesite (3) gabbro
(2) pegmatite (4) obsidian
Which graph best represents the relative densities of three different types of igneous
rock?
Which INTRUSIVE rock is approximately 30% Amphibole ?
(1) granite (3) basalt
(2) andesite (4) diorite
What is the approximate % of Plagioclase Feldspar
in a typical Andesite?
≈55%
How about the approximate % of Biotite in
a very FELSIC sample of Andesite?
≈ 18 %
≈ 8 % for a Mafic sample
Which intrusive igneous rock could be composed of approximately 60% pyroxene,
25% plagioclase feldspar, 10% olivine, and 5% amphibole?
(1) granite (2) rhyolite (4) basalt
(3) gabbro