Download Rocks and Minerals

Rocks and Minerals
Elements, Compounds and
Mixtures
• Matter is anything that takes up space and
has mass.
• All matter can be classified into three
forms: elements, compounds and mixtures.
Element
• An element is a substance that cannot be
separated into simpler substances by
ordinary chemical means. Scientists have
identified 109 elements.
• Each element has a name and a chemical
symbol made up of one or two letters.
• The smallest part of an element that has all
the properties of that element is an atom.
Molecules
• Some elements are made up of atoms that
are chemically combined to form
molecules.
• A molecule is two or more atoms held
together by chemical forces.
Atomic Structure
• Atoms are made up of three main particles:
protons, neutrons and electrons. The center
of the atom is called the nucleus. Two
different kinds of particles are found in the
nucleus. One of these is the proton.the
proton is a positively charged particle. The
other particle that makes up the nucleus is
the neutron. A neutron is a neutral particle.
Compounds
• A compound is made of atoms of different
elements that are bonded together. Water is
a compound. Some compounds are made
up of aluminum, magnesium, silicon,
oxygen and hydrogen.
Mixtures
• Some forms of matter are neither elements nor
compounds. Instead they are two or more
substances mixed together. Such forms of matter
are called mixtures. A mixture is two or more
substances physically combined. Most rocks, soil,
sea water and air are examples of mixtures.
Because the substances that make up a mixture are
not chemically combined they can be separated by
physical means.
Chemical Formulas
• The combinations of chemical symbols that
represent atoms are called chemical
formulas.
• A chemical formula shows that elements
that make up a compound. A chemical
formula also shows the number of atoms of
each element in a molecule or smallest
particle of the compound.
Subscripts
• Subscripts give the number of atoms of the
element in the compound. Subscripts are
placed to the lower right of the symbols.
Minerals
• A mineral is a naturally occurring, inorganic
solid that has a definite chemical
composition and crystal structure. In order
for a substance to be called a mineral, it
must have all of the characteristics
described in this definition.
Inorganic
• A mineral must be inorganic, or not formed
from living thing or the remains of living
things.
Solid
• A mineral is always a solid. Like all solids,
a mineral has a definite volume and shape.
Chemical Composition
• A mineral has a definite chemical
composition. A mineral may made of a
single pure substance, or element, such as
gold, copper or sulfur. Most minerals are
made of two or more elements chemically
combined to form a compound.
Crystal Structure
• A mineral’s atoms are arranged in a definite
pattern repeated over and over again.
Atoms not confined, the repeating pattern
of a mineral;s atoms forms a solid called a
crystal. A crystal has flat sides that meet in
sharp edges and corners. All minerals have
a characteristic crystal structure.
• There are 2500 different kinds of minerals.
Crystal Structure
Crystals
Formation and Composition of
Minerals
• Many minerals come from magma, the
molten rock beneath the Earth’s surface.
When magma cools, mineral crystals are
formed. How and where magma cools
determine the size of the mineral crystals.
When magma cools slowly beneath the
Earth’s crust, large crystals form. When
magma cools rapidly beneath the Earth’s
surface, small crystals form.
Crystal Formation
• Crystals may also form from compounds
dissolved in a liquid such as water.When
the liquid evaporates, or changes to a gas, it
leaves behind the minerals as crystals.
Halite, or rock salt, forms in this way.
Most Abundant
Elements
• The eight most abundant elements in the
Earth’s crust are oxygen, silicon, aluminum,
iron, calcium, sodium, potassium and
magnesium. There are about 100 common
minerals formed from the eight most
abundant elements.Of these 100, fewer than
20 are widely distributed and make up
almost all the rocks in the Earth’s crust.
Rock Forming Mineral Groups
Chemical Classification
Mineral
Elements
Silicates
Feldspar, Pyroxene,
Olivine, Mica, Quartz
Silicon, Oxygen
Carbonates
Calcite, Dolomite
Calcium Carbonate
Oxides
Hematite
Iron
Sulfates
Gypsum
Sulfur, Calcium
Halides
Halite
Sodium, Chlorine
Identifying Minerals
• Minerals have certain physical properties
that can be used to identify them, such as
color, luster, hardness, streak, density,
crystal shape, and other special properties.
Color
• The color of a mineral is an easily observed
physical property. Color can be used to
identify only those few minerals that always
have their own characteristic color, such as
malachite which is always green. The
mineral azurite is always blue.
• Many minerals come in a variety of colors.
Some are colorless.Colors can also change.
Color
The Many Colors of Quartz
Luster
• The luster of a mineral describes the way a
mineral reflects light from its surface.
Certain minerals have a metallic luster, such
as silver, copper and gold. Minerals that do
not reflect light have a nonmetallic luster,
and are described by terms like glassy,
pearly, dull and silky.
Metallic Luster
Non Metallic Luster
Hardness
• The ability of a mineral to resist being
scratched is known as its hardness.
Hardness is one of the most useful
properties for identifying minerals.
Friedrich Mohs, a German mineralogist,
worked out a scale of hardness for minerals
ranging from 1 to 10. The number one is
assigned to the softest mineral, talc and 10
is assigned to the mineral, diamond.
Moh’s Scale
1-10
Streak
• The color of the powder scraped off a
mineral when it is rubbed against a hard ,
rough surface is called its streak. The streak
may be different from the color of the
mineral. Streak can be observed by rubbing
the mineral sample across a piece of
unglazed porcelain, which is called the
streak plate. A streak plate has a hardness
slightly less than 7.
Streak
Density
• Density is the amount of matter in a given
space. The density of a mineral is always
the same, no matter what the size of the
mineral sample.
Crystal Shape
• Minerals have a characteristic crystal shape
that results from the way the atoms or
molecules come together as the mineral is
forming. There are six basic shapes of
crystal structures: cubic, hexagonal,
orthorhombic, monoclinic, tetragonal and
triclinic.
Crystal shape
Cleavage and Fracture
• The terms cleavage and fracture are used to
describe the way a mineral breaks. Cleavage
is the tendency of a mineral to split along
smooth, definite surfaces. Some minerals,
like halite, break into small cubes. Micas
cleave along one surface, making layers of
thin sheets. Most minerals do not break
along smooth lines.
Cleavage
Fracture
Special Properties
• Some minerals can be identified by special
properties. Magnetite is naturally magnetic.
Fluorite glows under ultraviolet light. Halite
tastes salty. Sulfur smells like rotten eggs.
Calcite fizzes when hydrochloric acid is
added to . Uraninite is radioactive.
Ores
• The term ores is used to describe minerals
or combinations of minerals from which
metals and nonmetals can be removed in
usable amounts.
Metals
• Metals are elements that have shiny
surfaces and are able to conduct electricity
and heat. Metals can be pressed or
hammered into thin sheets and other shapes
without breaking. Metals cans also be
pulled into thin strands. Iron, lead,
aluminum, copper, silver and gold are
examples of metals.
Smelting
• Most metals are found combined with other
substances in ores. After the ores are
removed from the Earth by mining, the
metals must be removed from the ores.
During a process, called smelting, an ore is
heated in such a way that the metal can be
separated from it. Metals are useful.
Copper is used in pipes and electrical wire.
Nonmetals
• Nonmetals are elements that have dull
surfaces and are poor conductors of
electricity and heat. Nonmetals are not
easily shaped. Some are removed from the
Earth in usable form. Others must be
processed. Sulfur,a nonmetal, is used to
make matches, fertilizers and medicines.
Gemstones
• Gemstones are minerals that are hard,
beautiful and durable and can be cut and
polished for jewelry and decoration. Once a
gemstone is cut and polished, it is called a
gem. The rarest and most valuable
gemstone- diamonds, rubies, sapphires and
emeralds, are known as precious stones. All
other gemstones, amethysts, zircons,
garnets, are known as semiprecious stones.
Rocks
• A rock is a hard substance composed of one
or more minerals. A rock can also be made
of or contain naturally occurring substances
that do not perfectly fit the definition of a
mineral. Rocks can be composed of
volcanic glass or of opal. Both of these
substances lack a crystalline structure.
Types of Rocks
• Geologists place rocks into three groups
according to how they form: igneous,
sedimentary and metamorphic.
Igneous Rocks
• Igneous rocks were originally hot, fluid
magma within the Earth. Igneous get their
name from the Latin word, ignis, which
means “fire”.
Sedimentary Rock
• Most sedimentary rocks are formed from
particles that have been carried along and
deposited by wind and water. These
particles, sediments or detritus, include bits
of rock in the form of mud, sand or pebbles.
Sediments also include shells, bones,
leaves, stems and other remains of living
things. Over time they are pressed together
to form rocks.
Detrital
• The rocks that form by cementation or
compaction are known as detrital or clastic
sedimentary rocks.
• They are further subdivided by size of the
particles.
Chemical Sedimentary
• Chemical sedimentary rocks form from
solution
• An example would be rock salt or gypsum.
Organic Sedimentary
• These sedimentary rocks form from the
remains of once living organisms or the
processes of living organisms.
• Coal is an organic rock formed from plants.
• Coquina or chalk from from sea creatures.
Weathering
• Rocks are broken down over by chemical
weathering or physical weathering.
• Chemical weathering, like acid rain, alters
the structure of a rock by adding or
removing an element.
• Mechanical weathering. Like frost wedging,
just breaks the rock into smaller pieces.
Weathering
• Quartz is resistant to weathering because it
is so hard. Sand on the beach is often little
pieces of quartz.
• Sedimentary rocks are often compacted and
cemented together. This process of making
a rock is known as lithification.
Cementation
• Cementation occurs when water carrying
minerals runs over the sediments and
deposits minerals that act like glue sticking
them together.
Compaction
• Compaction is the pressing together of
particles over time due to layers being
deposited again and again. The weight and
pressure pushes the small pieces together.
Erosion
• Erosion occurs when the small pieces are
carried away.
• The agents of erosion are running water,
waves, and wind.
Metamorphic Rocks
• Metamorphic rocks are formed when
chemical reactions, tremendous heat and
great pressure change existing rocks into
new kinds of rocks. These new rocks have
chemical and physical properties usually
quite different from the original rocks.
Rock Cycle
• The continuous changing of rocks from one
kind to another over long periods of time is
called the rock cycle. The rock cycle has no
definite sequence. It can follow many
different pathways.
Granite and the Rock Cycle
• Because granite is made of hard materials it is
resistant to nature’s forces. It can be slowly worn
down until bits of granite flake off and fall in
streams and are eventually reduced to sand. The
sand from granite, along with other sediments is
carried to the sea and is deposited on the floor.
The weight of layers piling on puts pressure on
lower layers and with calcite the granite becomes
part of a sedimentary rock. After many years,
under great pressure and temperature the
sedimentary rock will change to a metamorphic
rock, quartzite
Fluid and Fire: Igneous Rocks
• Igneous rocks are classified according to
their composition and texture.
• Composition refers to the minerals of which
rocks are formed.
• Texture means the shape, size, arrangement
and distribution of the minerals that make
up rocks.
• Both are evident in a rock’s appearance.
Igneous Rock Textures
• Igneous rocks have four basic types of
textures: glassy, fine-grained, coarsegrained and porphyritic.
Glassy Igneous
• Glassy igneous rocks are shiny and look
like glass. The minerals that make up a
glassy igneous rock are not organized into
crystals. Obsidian has a glassy texture.
Fine-Grained Igneous
• Fine-grained rocks, unlike glassy rocks, are
made of interlocking mineral crystals.
These crystals are too small to be seen
without the help of a microscope. The dark
gray rock known as basalt has a finegrained texture.
Coarse-Grained Rock
• Coarse-grained rocks, such as granite,
consist of interlocking mineral crystals,
which are all roughly the same size and
visible to the unaided eye.
Porphyritic Igneous Rocks
• Porphyritic rocks consist of large crystals
scattered on a background of much smaller
crystals. Sometimes these small
background crystals are too tiny to be seen
with a microscope. Porphyritic rocks have
a texture that resembles rocky road ice
cream.
Igneous Variety
• Where and how magma cools determines
the size of mineral crystals. The longer it
takes magma to cool, the larger are the
crystals that form. Glassy and fine-grained
rocks form from lava that erupts from
volcanoes and hardens on the Earth’s
surface. Coarse-grained rocks form from
molten rock that cools and hardens within
the Earth.
Extrusive Rocks
• Rocks formed from lava are called extrusive
rocks. Because lava is brought to the
surface by volcanoes, extrusive rocks are
also known as volcanic rocks. Basalt and
obsidian are two kinds of extrusive rocks
that are quite solid. Pumice, another
extrusive rock, is filled with bubbles.
Intrusive Rocks
• Igneous rocks formed deep within the Earth are
called intrusive. They form when magma forces
its way upward into preexisting rocks and then
hardens. Intrusive rocks include granite and
pegmatite. Intrusive rocks are also known as
plutonic rocks. A mass of intrusive rocks are
known as a pluton. Plutons may produce
landforms by pushing up layers of rock above
them, such as domes.
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Slowly Built Layers:
Sedimentary Rocks
• Igneous rocks are the most common rocks
on Earth but most of them exist below the
surface. 75% of the rocks exposed at the
surface are sedimentary.
Classification of Sedimentary
Rocks
• The most widely used classification system
for sedimentary rocks places them into three
main categories according to the origin of
the materials from which they are made.
These three categories are: clastic or
detrital rocks, organic rocks and chemical
rocks.
Clastic Rocks
• Sedimentary rocks that
are made of the
fragments of
previously existing
rocks are known as
clastic rocks. Clastic
rocks classified
according to the size
and shape of the
fragments in them:
conglomerate,
sandstone and shale.
Conglomerates
• Some clastic rocks are made of rounded
pebbles cemented together by clay, mud or
sand. If over a third of the rock is made of
pebbles, the rock is called a conglomerate.
The pebbles in conglomerates are smooth
and rounded because they have been worn
down by the action of water. They are also
called puddingstones. If the pieces of the
rock are angular then it is called breccia.
Sandstones
• Clastic rocks made of small, and-sized
grains are called sandstones. At least half
the particles in a clastic rock must be sand
sized in order for it to be considered a
sandstone. Sandstones are very common
rocks. They are formed from the sand on
beaches, in riverbeds and in sand dunes. In
a sandstone, the grains are cemented
together by minerals such as quartz, calcite
and hematite, that harden.
Shale
• Many geologists use term shale to describe
all the clastic rocks that are made of
particles smaller than sand. Shale forms
from small particles of mud and clay that
settle to the bottom of quiet bodies of water
such as swamps. Most shale can be split
into flat pieces.
Organic Rocks
• Organic rocks come from
organisms. Limestone are
often but not always
organic rocks. Deposits of
limestone may be formed
from the shells of
creatures when they die.
Creatures may also
cement their shells
together and over time
form reefs. Coal is also
made from the remains of
living things. It is made
from plants that lived
millions of years ago.
Coal and Coquina
Chemical Sedimentary Rocks
• Water precipitates two ways to form
chemical sedimentary rocks
• 1. by the process of evaporation
• 2. through the life processes of marine
organism
Biochemical Sedimentary Rocks
• Coral is an example of
a chemical
sedimentary rock that
was formed through
the life processes of a
coral polyp.
Evaporites
• Halite and gypsum are
examples of
evaporites.
Chemical Rocks
• Some sedimentary rocks
are formed when a sea or
lake dries up, leaving
large amounts of minerals
that were dissolved in
water. Examples of
chemical rocks formed
this way include rock salt
and gypsum. Some
limestone rocks are
formed by inorganic
processes in caves. As
water evaporates, a thin
deposit of limestone is left
behind.
Limestone- the most abundant
sedimentary rock
• Calcium carbonate is
carried in solution in
ocean water. When the
calcium carbonates comes
out of solution as calcite,
the crystals grow together
and lime stone forms.
Limestone is 50% calcite.
Much is found in Kansas
which was underwater.
Rock Salt
When water that is rich in
salt evaporates, it deposits
the mineral halite. Halite
forms rock salt. Rock salt
deposits can be as thick as
400 meters. Companies
mine these salts. It is used
in making glass, paper,
soap and dairy products.
The halite is processed for
table salt.
Inorganic Chemical Sedimentary
Rocks
• Travertine is an
inorganic chemical
sedimentary rock that
is found in caves.
Silicates
• Chert, jasper and flint
all form from silica
that is left behind
when water
evaporates.
Sedimentary Rock Classification
Changes in Form: Metamorphic
Rocks
• When already existing rocks are buried
deep within the Earth, tremendous heat,
great pressure and chemical reactions may
cause them to change into different rocks
with different textures and structures. The
changing of one type rock into another as a
result of heat, pressure and /or chemical
reactions is called metamorphism.
Metamorphic Rocks
• Metamorphic rocks may be formed from
igneous, sedimentary or metamorphic rocks.
Heat and pressure are great enough to make
tock undergo change. Temperatures of 100
degrees to 800 degrees cause some minerals
to break down, allowing their atoms to form
other more heat-tolerant minerals.Texture,
mineral and chemical composition may
change.
Metamorphic Rocks
• The amount of heat, pressure and chemical
reactions varies during metamorphism.
Thus the degree of metamorphism also
varies. The characteristics of the original
rock also affect the degree of
metamorphism. Many metamorphic rocks
can be produced from more than one kind
of rock.
Metamorphic Classification
• Like igneous and sedimentary rocks,
metamorphic rocks can be classified
according to texture. The classification for
metamorphic rocks are based on the
arrangement of the grains that make up the
rocks.
Foliated Rocks
• In the first group, the mineral crystals are
arranged in parallel layers, or bands. The
word foliated comes from the Latin word
for leaf. It describes the layers in such
metamorphic rocks, which are thin and flat.
Most metamorphic rocks are foliated, like
schist, slate and gneiss.
Unfoliated Rocks
• In the second, smaller group of
metamorphic rocks, the rocks are not
banded and do not break into layers. These
rocks are said to be unfoliated. Marble and
quartzite are examples of unfoliated rocks.