Transcript Rocks

Classifying
Rocks
6.E.2.1 Summarize the structure of the Earth,
including the layers, the mantle and
core based on the relative position,
composition and density.
Rocks
• Are made of mixtures of minerals and other
materials, although some may contain only a
single mineral.
– Granite
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Quartz
Feldspar,
Mica
Hornblend
Rocks
• When examining a rock, you must look at the
inside of the rock because the effects of ice,
liquid water, and weather can change the
outer surface of the rock.
• When studying a rock sample, geologists
observe the rock’s mineral composition, color,
and texture.
Mineral Composition
• About 20 minerals make up most rocks of
Earth’s crust. The minerals are known as rockforming minerals.
• A rock’s color provides clues to the rock’s
mineral composition. For example, granite is
generally a light-colored rock that has high
silica content. Basalt is a dark-colored rock
that is low in silica.
Mineral Composition
• Geologist observe the shape and color of
crystals in a rock to identify the minerals that
the rock contains.
• In identifying rocks, geologists also use some
of the tests that are used to identify minerals.
• Acid tests are used to test for carbonates.
• Magnetic tests are used to test for iron and
nickel.
Characteristics
Group A
Group B
Rock Color Texture
Group C
Luster
Group D
Group E
Group F
Density
Hardness
Porous
Texture
• As with minerals, color alone does not provide
enough information to identify a rock. But a
rock’s texture is very useful in identifying a
rock. Most rocks are made up of particles of
minerals or other rocks, which geologists call
grains. Grains give a rock its texture. To a
geologist, a rock’s texture is the look and feel
of the rock’s surface. Some rocks are smooth
and glassy. Others are rough or chalky.
Texture
• Size, shape and pattern of rock grains.
– Grains- particles of minerals or other rocks.
Texture (Grain Size)
• Course Grained- Large and easy to see.
• Fine Grained- small.
Texture (Grain Shape)
• Grains vary widely.
– Tiny particles of sand.
– Look like seeds
– Crystals
– Smooth / rounded
– Jagged
Texture (Grain Pattern)
• Grains often form patterns.
– Some lie in flat layers.
– Rows of grains.
– Random grains.
Texture (No Visible Grain)
• Have no grain.
– They cool very quickly
when they form, gives the
rock a smooth, shiny
texture like thick glass.
(obsidian)
– Or made out of extremely
small particles of silica that
settle out of water. (flint)
Origin
• 3 Groups- refers to how the rocks formed.
Igneous
Sedimentary
Metamorphic
• Forms from
cooling
molten rock.
• Magmabelow the
surface.
• Lava- above
the surface.
• Forms from
particles of
other rocks,
remains of
plants and
animals that
are pressed
and cemented
together.
• Forms from
pre-existing
rock, deep
underground.
• Changes rock
with heat,
pressure and
chemical
reactions.
Rock Cycle
Questions
A rock’s _________ provides clues to the rock’s
mineral composition.
A. shape
B. size
C. color
D. diameter
What gives a rock its texture?
A. Grains
B. Color
C. Size
D. None of the above
What the three basic types of rocks?
A. Microscopic, Normal, & Gigantic
B. Igneous, Settlement, & Metamorphic
C. Igneous, Sedimentary, & Metabolism
D. Igneous, Sedimentary, & Metamorphic
The End