Earth Science Chapter 3 Minerals and Rocks. Minerals A mineral is a naturally occurring, solid,...

Earth ScienceEarth Science

Chapter 3Chapter 3

Minerals and RocksMinerals and Rocks

MineralsMinerals

• A mineral is a naturally occurring, solid, inorganic substance that has a definite chemical composition and molecular structure.– Naturally occurring means not made artificially– Inorganic means it is not now, nor ever has

been alive.

• Minerals are classified on the basis of their physical and chemical properties.

Mineral CharacteristicsMineral Characteristics

• The physical properties of a mineral are due largely to the internal arrangement of atoms.

• The six key physical properties that can be seen or easily tested are: color, streak, luster, hardness, and cleavage or fracture.


• Color – Most visible property– Color alone is not a good mineral identifier.

• Many minerals exhibit the same color.• Many minerals are found in a variety of colors.


• Streak– The color of a mineral in its powdered form.– Streak is reliable for mineral identification.

• Streak may be different from mineral color.


• Luster– The way in which light is reflected from the

surface of a mineral.– Minerals with metallic luster shine like

polished metals.– Minerals with nonmetallic luster have no

metallic shine.• Nonmetallic lusters can be glassy, dull,

earthy, etc.


• Metallic lusters

• Nonmetallic lusters


• Hardness– A mineral’s resistance to being scratched– The relative hardness of a mineral is

determined by comparing it to the hardness of ten “standard” minerals that make up Moh’s Hardness Scale.

– Minerals are often compared to the hardness of glass (5.5).


• Cleavage– The tendency of a mineral to split along one

or more smooth surfaces or planes.

Mica (1 plane) Halite (3 planes)


• Fracture– Minerals that don’t show cleavage, fracture

unevenly when they break.


• Other properties Magnetic React with Acid

Salty Taste Bad Odor

Formation of MineralsFormation of Minerals

• All minerals are crystalline, or made up of atoms arranged in a pattern.

• Minerals are grouped according to their chemical composition. – All minerals are made up of elements.– Minerals are classified based upon the

elements they contain.– Most common minerals in the crust are

silicates (made of silicon and oxygen).

Formation of MineralsFormation of Minerals

– Of all the minerals on the Earth’s crust, over 90% are a combination of the following eight elements:

Percent By Mass in CrustOxygen 46.4 %

Silicon 28.2%

Aluminum 8.2%

Iron 5.6 %

Calcium 4.2%

Sodium 2.4%

Magnesium 2.3%

Potassium 2.1%

Others 0.6%

RocksRocks

• Most rocks are composed of one or more minerals.– Rocks composed of one mineral are called

monominerallic.– Rocks composed of more than one mineral

are called polyminerallic.

• Most rocks have a number of minerals in common.– Of the over 2,500 different minerals, only 10

to 15 minerals compose 90% of rocks.

RocksRocks

• Differences between rocks and minerals– Minerals have a uniform composition while

the physical properties of rocks vary from one rock to the next.

– Minerals are classified by physical properties while rocks are classified by their origin.• Igneous - solidification of molten rock• Sedimentary - compaction and cementation

of sediments• Metamorphic - recrystalization of rock

Igneous RocksIgneous Rocks

• Igneous rocks form as a result of the solidification of molten rock material.– Molten rock beneath the Earth’s surface is

called magma.– Molten rock that reaches the Earth’s surface

is called lava.

• When molten rock solidifies, it crystallizes into igneous rock.


• The texture, or grain appearance, depends on the size and arrangement of crystals.– Intrusive igneous rocks:

• Form from magma underground• Solidify slow & have large crystals

– Extrusive igneous rocks:• Form from lava above ground• Solidify quick & have small crystals


• Igneous rocks are grouped according to their mineral composition. – Felsic igneous rocks

• Light color• Low density• Most common on continents

– Mafic igneous rocks• Dark color• High density• Most common on ocean floor

Sedimentary RocksSedimentary Rocks

• Sedimentary rocks form as a result of compaction and cementation of sediments.– Sediments are changed into rock after they

are transported and deposited.– Most sedimentary rocks are deposited in large

bodies of water.– The presence of sedimentary rocks suggests

area was underwater at time of formation.


• Compaction– Pressure created by water and overlying

sediments can force particles of sediment close together and compress them into rock.

• Cementation– The addition of minerals, such as silica, lime, or

iron oxide, tends to glue rock particles together to form solid rock.


• Clastic Sedimentary Rock– Formed from sediments made up of rock

fragments held together by cement– Layers or cementing material are often visible


• Chemical or Crystalline Sedimentary Rocks– Form as a result of chemical processes

• Water with dissolved minerals evaporates• Minerals that precipitate out forms crystals

Rock Salt Rock Gypsum


• Bioclastic or Organic Sedimentary Rocks– Form from remains of dead organisms.

• Coal forms as a result of compression of plant remains.

• Limestone can be made of shells. Coal Limestone

Metamorphic RocksMetamorphic Rocks

• Metamorphic rocks form as a result of recrystallization of unmelted material under conditions of high temperature and pressure over long periods of time.– Recrystallization is a process in which rocks

undergo change without true melting.– As a result of heat and pressure minerals in

the rocks combine to form new, larger, denser crystalline structures.


• Banding and foliation of minerals are the most outstanding characteristic of metamorphic rocks.– Due to concentrations of various minerals into

zones of different colors– Not to be confused with layering of

sedimentary rocks


• Types of Metamorphism– Contact metamorphism

• Molten rock comes in contact with nearby rock • Heat from magma alters the rock it touches

– Regional metamorphism• Large areas of rock are under intense heat

and pressure• Generally associated with mountain building

The Rock CycleThe Rock Cycle

• The rock cycle describes how rocks of all types can be changed into other rocks.– Earliest rocks formed on Earth were igneous– They were uplifted, weathered, and eroded to

form sediments.– The sediments were deposited, buried and

compacted into sedimentary rocks.– Sedimentary and igneous rocks were subject to

heat and pressure to form metamorphic rocks.

Mineral ConservationMineral Conservation

• Today the world’s need for energy resources is greater than ever.– Most energy sources-coal, oil, and natural

gas-are nonrenewable (used faster than they can be replaced).

– Coal oil and natural gas are called fossil fuels because they are made of the remains of plants and animals that lived long ago.

– Fossil fuels and other nonrenewable resources are vital to our everyday lives.

Mineral ConservationMineral Conservation

– Alternate sources of renewable energy resources are under development. • Water power• Wind power• Solar energy• Geothermal energy

– The use and distribution of mineral resources have global, financial and political implications.

– THEY MUST BE USED WISELY.

Earth Science Chapter 3 Minerals and Rocks. Minerals A mineral is a naturally occurring, solid,...

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Transcript of Earth Science Chapter 3 Minerals and Rocks. Minerals A mineral is a naturally occurring, solid,...