The rocks you see around you - the mountains, canyons &
riverbeds, are all made of minerals.
A rock is made up of 2 or more minerals.
Think of a chocolate chip cookie as a rock.
The cookie is made of flour, butter, sugar & chocolate.
The cookie is like a rock and the flour, butter, sugar &
chocolate are like minerals.
You need minerals to make rocks, but you don't need rocks
to make minerals.
All rocks are made of minerals.
Rocks are mixtures of minerals (grains) cemented and pressed
together
Most rocks are composed of at least 2 minerals
Example of a rock:
Granite: contains 75% feldspar, 20% quartz, and 5% mica
Color and TEXTURE to determine the rocks
mineral composition.
TEXTURE:
Grain size: coarse grained- easy to see
fine grained- need a
microscope to see.
no grain- texture similar to
glass
Texture: physical features, how
the grains of the rock are arranged
Grain: particles of minerals that make
up the rock
Rocks are classified by how they formed and
what they’re made of
There are 3 general classes of rocks
Igneous Rocks…are formed when lava and
magma crystallize to form solid rock
Metamorphic Rocks…are formed when an
existing rock is partially melted, squeezed, or
both
Sedimentary Rocks…are formed when
sediments (sand clay, and silt) are compressed
and become solid rock
Igneous Rocks
Extrusive: Cools outside the
earth- very small crystals
glassy: fine or no grain
Intrusive: Cools inside the
earth- large crystals easy to
see: coarse grain
SILICA: contained in most of the Earth’s Rocks…
Otherwise know as Quartz….
If an Igneous rock is light in color…
than it is high in silica
If an Igneous Rock is dark in color
than it is low in silica
Uses of Igneous Rocks…
Tools and building materials
Granite is used for building materials, statues
and bridges
Basalt=gravel
Sedimentary Rock
EROSION: Rocks are eroded into sediment
DEPOSITION: Sediment is deposited onto the
Earth
COMPACTION: Over millions of years, layers of
sediment build up and press together
CEMENTATION- Minerals in the rock dissolve
into water. Water seeps in between sediment
particles. Dissolved minerals recrystalize and
“GLUE” the sediment together.
Sedimentary Rock can be organic or
inorganic…..
Most of the world’s ocean floors contain
limestone that formed from the shells of dead
marine organisms
Sedimentary rock can be Clastic. Clastic is
when rock fragments are squeezed together
Conglomerate: pebbles are glued together
Breccia: Sharp fragments of rocks are glued
together
Sedimentary Rocks can be CHEMICAL
Chemical means that the rock is formed from
the evaporation of water - the resulting rock is
called a Chemical rock
USES of sedimentary rock….
Building materials (The White House is built of
sandstone)
Limestone:
makes cement
The Origin of Metamorphic rock:
Rocks that have changed due to…
HEAT AND PRESSURE!!!!
Causes changes in the composition of the rock
Metamorphic Rocks are classified by:
FOLIATED: minerals line up and form bands
Non-FOLIATED: minerals change but don’t
form bands