Rocks and Minerals Study Guide
Name _________________________
The test will be given on Friday, November 6th.
Continental Drift
Remember that Wegener’s Theory of Continental Drift states that the continents
were once joined together as a super-continent called Pangaea. Besides the
puzzle-like fit of the continents, the best evidence for his theory includes similar
types of rocks and fossils, the remains of a plant or animal that have been cast in
rock.
Minerals
Minerals are
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Naturally occurring
Inorganic (nonliving)
Solid
Things that have a definite composition and crystalline structure
Minerals are identified by using their properties.
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Color
Luster – the way in which a mineral reflects light
Streak – the color of the powder of a mineral
Cleavage – the splitting of a mineral along smooth, flat surfaces
Fracture – the manner in which a mineral breaks along either curved or
regular surfaces
 Hardness – a measure of the ability of a mineral to resist scratching;
Diamond is the hardest mineral; Talc is the softest mineral
 Density – the ratio of the mass of a substance to the volume of a substance;
“how much stuff is packed into a certain amount of space”
Graphite is a mineral used to make pencil lead.
Rocks
The most useful way to identify a rock is by its mineral content. Different colors
in rocks are due to the different minerals in them.
Rocks are classified by how they are formed, and there are three types of rocks –
sedimentary, igneous, and metamorphic. One type of rock can be changed into
another by undergoing the rock cycle. When old rock is changed into new rock
during the cycle, it takes a very LONG time. Not all rocks go through the entire
cycle.
Sedimentary Rocks
Sedimentary rocks are formed by weathering (when wind, water, and ice break
down rocks into sediment), erosion (when soil and sediment is moved from one
place to another), and deposition (the process in which material is laid down).
Layers of sediment are pressed and cemented together to form sedimentary rock.
Most fossils are found in sedimentary rock.
Sandstone is an example of a sedimentary rock.
Igneous Rocks
Igneous rock forms when hot, liquid rock, or magma, cools and solidifies. (Magma
is formed underground, but it is called lava when it reaches the surface.)
Volcanos are associated with igneous rocks.
 Intrusive igneous rock is formed beneath the Earth’s surface. Because of
the slow cooling time, large crystals are formed.
 Extrusive igneous rock is formed on the Earth’s surface, and since it cools
quickly, very small or no crystals are formed.
Stone Mountain is made of Granite, an igneous rock.
Metamorphic Rocks
Metamorphic rocks are rocks in which the structure, texture, or composition have
changed. Metamorphic rocks are formed by extreme heat and pressure. Marble
is an example of a metamorphic rock.
Fossils
Studying fossils helps us learn how the Earth’s environment has been changed. In
large sections of sedimentary rock, the oldest fossils will be found in the bottom
layer.
Sometimes fossils from ocean animals are found on tops of mountains! That
means that the mountain was once covered by the ocean a very long time ago
and the mountain was raised up due to the movement of lithospheric plates.
Fossil Fuels
Fossil fuels can be obtained by surface mining, strip mining (removing long strips
of overlying soil and rock), and drilling wells.
The energy found in fossil fuels originally came from the Sun.
Petroleum and natural gas form mainly from decayed sea organisms.
Smog is the photochemical base formed when sunlight acts on industrial
pollutants and burning fuels.