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ROCKS & MINERALS
The Building Blocks of Earth
ROCKS VS. MINERALS

Rock is an indefinite mixture of naturally
occurring substances, mainly minerals.
 Its
composition may vary in containment of
minerals and organic substances, and are never
exact.
ROCKS VS. MINERALS

A mineral is any naturally occurring,
inorganic substance, often characterized by
an exact crystal structure.
 Its
chemical structure can be exact, or can vary
within limits.
 Elements that occur naturally are also
considered minerals.
MINERAL GROUPS
All minerals belong to a chemical group:








Elements,
Sulfides,
Oxides,
Halides,
Carbonates,
Nitrates,
Borates,
Chromates,







Sulfates
Phosphates,
Arsenates,
Vanadates,
Tungstates,
Molybdates, and
Silicates.
THREE TYPES OF ROCKS
Sedimentary Rocks
 Igneous Rocks
 Metamorphic Rock

SEDIMENTARY ROCK

For thousands of years, little pieces of our earth have
been eroded--broken down and worn away by wind
and water.

These little bits of our earth are washed downstream
where they settle to the bottom of the rivers, lakes,
and oceans and deposited in layers on top of each.

These layers are pressed down more and more
through time, until the bottom layers slowly turn into
rock.
CLASTIC ROCKS
Sediments may also include pieces of stones
and shells and other objects, not just grains of
pure minerals.
 Geologists use the word clasts to denote
particles of all these kinds, and rocks made of
clasts are called clastic rocks.

MARINE ORGANIC ROCKS

Microscopic plankton build shells out of
dissolved calcium carbonate or silica.

When these plankton die, their bodies
accumulate in thick layers on the seafloor.
 Limestone
(carbonate) and chert (silica).
BOTANIC ORGANIC ROCK

Dead plant material builds up into thick layers.
With a small degree of compaction, this
becomes peat and after much longer and
deeper burial, it becomes coal.
COAL

Although peat is forming in parts of the world
today, the great beds of coal we mine formed
during past ages in enormous swamps.
 There
are no coal swamps around today, because
conditions do not favor them.
CHEMICAL ROCKS

As ancient shallow seas began to dry and
become more concentrated, minerals begin
to precipitate.


Calcite (CaCO3), gypsum (CaSO4. 2H2O), and
halite (NaCl).
The resulting rocks are certain limestones or
dolomites, gypsum rock, and rock salt
respectively.

Part of the evaporite sequence.
SEDIMENTARY ROCK
Sandstone
 Limestone
 Gypsum
 Conglomerate
 Shale

SANDSTONE

Sandstone rocks are sedimentary rocks
made from small grains of the minerals
quartz and feldspar. They often form in
layers as seen in this picture. They are
often used as building stones.
LIMESTONE

Limestone rocks are sedimentary rocks
that are made from the mineral calcite
which came from the beds of evaporated
seas and lakes and from sea animal
shells. This rock is used in concrete and is
an excellent building stone for humid
regions.
SHALE

Shale rock is a type of sedimentary rock formed
from clay that is compacted together by
pressure. They are used to make bricks and
other material that is fired in a kiln.
CONGLOMERATE

Conglomerate rocks made up of large
sediments like sand and pebbles. The
sediment is so large that pressure alone
cannot hold the rock together; it is also
cemented together with dissolved minerals.
GYPSUM

Gypsum rocks are sedimentary rocks made up
of sulfate mineral and formed as the result of
evaporating sea water in massive prehistoric
basins.

It is very soft and is used to make Plaster of
Paris, casts, molds, and wallboards
METAMORPHIC ROCKS

Metamorphic rocks are igneous or sedimentary
rocks that have "morphed" into another kind of
rock.

How do sedimentary and igneous rocks
change?
 The
rocks are under tons and tons of pressure,
which fosters heat build up, and this causes them
to change.
FOUR AGENTS OF METAMORPHOSIS
Heat
 Pressure
 Fluid Content
 Strain

METAMORPHIC ROCK

Schist

Gneiss
SCHIST

Schist rocks are metamorphic formed
from basalt, shale, or slate, a
metamorphic rock. Through tremendous
heat and pressure, these rocks were
transformed into this new kind of rock.
GNEISS

Gneiss rocks are metamorphic that may
have been granite, but heat and pressure
changed it. The mineral grains in the rock
were flattened through tremendous heat
and pressure and are arranged in
alternating patterns.
IGNEOUS

Igneous rocks are formed either underground
or above ground from the cooling and
crystallization of magma.
 Extrusive
(aboveground)
 Intrusive
(below ground)
 Plutonic
(deep magma)
IGNEOUS MINERALS

The main minerals in igneous rocks are:
 feldspar
(silicates)
 quartz
(SiO2)
 olivine
(Mg and Fe silicates)
 mica
(sheet silicates)
INTRUSIVE IGNEOUS ROCK

Intrusive igneous rocks are formed when
magma, becomes trapped in small pockets. As
these pockets of magma cool slowly
underground, the magma forms igneous rocks.
 Intrusive
rocks cool more slowly (over thousands of
years) and have small to medium grains.
DEEP INTRUSIVE IGNEOUS ROCK

Igneous rock formed from deep magma is
called plutonic.
 Plutonic
rocks cool over millions of years, deep
underground, and can have grains as large as
pebbles and even a meter across.
EXTRUSIVE IGNEOUS ROCK
Igneous rocks are also formed when volcanoes
erupt, causing the magma to rise above the
earth's surface.
 When magma appears above the earth, it is
called lava. Igneous rocks are formed as the
lava cools above ground.

 Extrusive
rocks cool quickly (over periods of
seconds to months) and have invisible or very small
grains.
IGNEOUS ROCK
Granite
 Scoria
 Pumice
 Obsidian

FAMOUS ROCK STARS

The two best-known igneous rock types are
basalt and granite.
 Basalt
is the dark, fine-grained rock from lava flows
and magma intrusions. Its dark minerals are rich in
magnesium (Mg) and iron (Fe).
 Granite
is the light, coarse-grained rock formed at
depth and exposed after deep erosion. It is rich in
feldspar and quartz (silica).
BASALT
Basalt is a common extrusive volcanic rock. It is
usually gray to black and fine-grained due to
rapid cooling of lava at the surface of a planet.
 It may be porphyritic containing larger crystals
in a fine matrix, or vesicular, or frothy scoria.

GRANITE

Granite rocks are igneous rocks which were
formed by slowly cooling pockets of magma that
were trapped beneath the earth's surface.

Granite is used for long lasting monuments and
for trim and decoration on buildings.
SCORIA

Scoria rocks are igneous rocks which were
formed when lava cooled quickly above ground.
You can see where little pockets of air had
been. Scoria is actually a kind of glass and not
a mixture of minerals.
PUMICE

Pumice rocks are igneous rocks which
were formed when lava cooled quickly
above ground. You can see where little
pockets of air had been.
PUMICE

Pumice rock is so light, that many will actually
float in water. Because this rock is so light, it is
used quite often as a decorative landscape
stone. Ground to a powder, it is used as an
abrasive in polish compounds and in Lava©
soap.
OBSIDIAN

Obsidian rocks are igneous rocks that
form when lava cools quickly above
ground. Obsidian is actually glass and not
a mixture of minerals. The edges of this
rock are very sharp.
GEOLOGIC PROCESSES

The San
Andreas Fault is
an example of a
transform fault.
Figure 15-5
WEARING DOWN AND BUILDING UP THE
EARTH’S SURFACE

Weathering
is an external
process that
wears the
earth’s
surface
down.
Figure 15-6
Parent material
(rock)
Biological
weathering
(tree roots and
lichens)
Chemical
weathering
(water, acids,
and gases)
Particles of parent material
Physical weathering
(wind, rain, thermal
expansion and
contraction, water
freezing)
Fig. 15-6, p. 340
MINERALS, ROCKS, AND THE ROCK CYCLE

The earth’s crust consists of solid inorganic
elements and compounds called minerals
that can sometimes be used as resources.
 Mineral
resource: is a concentration of
naturally occurring material in or on the earth’s
crust that can be extracted and processed into
useful materials at an affordable cost.