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Transcript
Mineral vs. Rock
A rock is a solid combination of minerals or mineral
materials.
• Minerals are inorganic, meaning that living things did
not produce them and they occur naturally.
• Geologists don’t classify coal as a mineral because coal
was created from plant remains.
• Materials like brick and concrete are not considered
minerals either.
• Minerals are the building blocks of rocks
Mineral vs. Rock
Granite is made up of
quartz, feldspar, mica,
and hornblende.
A magnified view reveals
the individual crystals of
the minerals that make
up granite.
Mica
Quartz
Hornblende
Feldspar
Types of Rocks
 Rocks are classified into three major groups—
igneous, sedimentary, and metamorphic—based
on how they form.
Classifying Rocks
The size, shape, and arrangement of the crystals and
other particles that make up a rock give the rock its
texture.
A rock’s texture reveals what the rock is made from and
how and where it formed.
Igneous Rocks
 Igneous rock forms when molten material cools and
solidifies either inside Earth or at the surface.
Igneous
 An igneous rock is a rock that forms from magma.
 Magma is a mixture of molten rock and gases,
including water vapor, which forms underground.
 Magma that flows out of volcanoes is called lava.
Igneous
An igneous rock that forms
underground from hardened magma
is called an intrusive rock.
Intrusive rocks = cool slowly
underground = large crystals = coarse
texture.

An igneous rock that forms at
Earth’s surface is called an extrusive
rock.
Extrusive
igneous rocks = cool very
quickly at the surface = small crystals =
fine-grained texture.
Igneous
 Basalt is a fine-
grained, extrusive
rock. As this basalt
cooled, the rock
formed into
hexagonal columns.
Igneous
An igneous rock’s color gives a clue to its mineral
composition.
• Ex: Gabbro, an intrusive rock, and basalt, an extrusive
rock formed from magma rich in iron and magnesium.
The rocks are dark and dense.
• Ex: Granite is a coarse-grained, intrusive rock with a
high silica content. Granite is less dense and lighter in
color than basalt and gabbro.
Sedimentary Rocks
 A sedimentary rock is a rock that forms over time as
sediment is squeezed and cemented together.
 Geologists classify sedimentary rocks into three main
groups according to how they form: clastic rocks,
chemical rocks, and organic rocks.
Sedimentary
Sediment consists of small, solid pieces of material
that comes from rocks or living organisms.
• The process of weathering breaks down rock at Earth’s
surface, turning it into smaller pieces.
• Minerals dissolved in water are also sediment.
Sedimentary
 Sediment is often carried away by running water or
wind to a new location, where it is deposited in layers.
 As sediment piles up, the pressure causes the deeper
sediment to be compressed.
 Dissolved minerals in the water seep into the space
between particles of sediment and form a kind of
cement.
Sedimentary
 Colorful layers of
sandstone, like those
in this Utah canyon,
formed over millions
of years as water and
wind laid down
sediment.
Sedimentary
Clastic Rock
Sedimentary rocks that form from the broken fragments
of other rocks are called clastic rocks.
The fragments that make up clastic rocks are usually
held together by cement.
Sedimentary
Clastic rocks are classified mainly based upon the
average size of the fragments that they contain.
• EXAMPLES:
• Conglomerate is made of gravel and pebbles.
• Breccia is made up of sharp-edged fragments.
• Sandstone is formed from grains of sand.
• Mudstone is made primarily of mud or silt.
• Shale is mudstone made of flat grains aligned so that the
rock can split into sheets.
Sedimentary
 Conglomerate is a sedimentary rock in which rounded
pieces of other rocks are cemented together.
Sedimentary
Chemical Rock
Chemical sedimentary rocks form when minerals
precipitate out of solution.
• Rainwater dissolves many minerals on the land. These
dissolved minerals are then carried into the ocean.
• As water evaporates from the ocean surface, the
concentration increases until the minerals precipitate.
Sedimentary
 The strangely shaped rocks in Mono Lake, California,
are made of tufa, a chemical rock composed of calcium
carbonate.
Sedimentary
Organic Rock
Some rocks form as the result of organic processes.
• Marine animals extract calcium carbonate from ocean
water to form their shells and skeletons.
• The shells and skeletons sink to the ocean floor.
• The fragments compact and cement together, forming
limestone.
Sedimentary
 The cliffs of Dover on the southern coast of England
are composed of chalk, a type of fine-grained organic
limestone.
Metamorphic Rock
 Metamorphic rock is rock that has been changed by
temperature, pressure, or reactions with hot water.
 Most metamorphic rocks form under high temperatures
and pressures deep underground.
Metamorphic
Metamorphism can result in a rock with a mineral
content that is different from that of the original
rock.
• Heat deep inside Earth allows the minerals to
recrystallize, and small crystals to enlarge.
• Chemical changes occur, and new minerals may replace
the original minerals.
Shale
Slate
Schist
Gneiss
Rock Cycle
 The rock cycle is a series of processes in which rocks
continuously change from one type to another.
Rock Cycle
Constructive forces form new igneous rock.
Destructive forces break down rock, forming sediment.
Other forces push rock deep beneath the surface, where
heat and pressure form metamorphic rock.
Rock Cycle
 Depending
on their
pathway
through the
cycle, rocks
can wear
away,
undergo
Cooling
metamorphi
sm, or melt
and form
new igneous
rock.
Weathering &
Erosion
Compacting &
Cementation
Weathering
& Erosion
Melting
Heat &
Pressure
Melting
Heat &
Pressure