Substances composed of minerals.
Rocks are made from many minerals, so we CANNOT test properties! Instead, rocks are defined by HOW they form (Environment of Formation).
Let’s start with Igneous Rocks…
Form from solidified lava or magma. Igneous Rocks Form from solidified lava or magma.
The flowchart below illustrates the change from lava 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 from melted 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
light-colored metamorphic fine-grained igneous In addition to ash, solid rock formed on Mt. Hekla from the lava extruded during an eruption. This rock is most likely Mt. Hekla light-colored metamorphic fine-grained igneous (3) dark-colored metamorphic (4) coarse-grained igneous
MAFIC FELSIC
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
(1) granite (2) rhyolite (4) basalt (3) gabbro 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