Transcript Earth`s Surface 2.3

MINERALS ARE VALUABLE
RESOURCES
Minerals are basic building blocks of
Earth.
Minerals have many uses in industry and in the arts.
• Necessary to our modern way of life
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Sources of metals for cars and airplanes
Quartz and feldspar for glass
Fluorite and calcite for toothpaste
Silver compounds for photographic film
Mica and talc for paint
• Birthstone tradition is hundreds of years old
• Ancient Egyptians used gems (particularly beautiful minerals)
in jewelry at least 4000 years ago
• Found rough and irregularly shaped in nature
– Gem cutter grinds it into the desired shape and polishes it.
– Increases beauty and sparkle.
– Material used to shape and polish a gemstone must be at least as
hard as the gemstone itself.
• Metals are used in jewelry making and other decorative arts.
• Gold and silver are usually combined with copper to increase
their hardness
Minerals form in several ways.
• Minerals form by natural processes within Earth or on
Earth’s surface
– Develop when atoms of one or more elements join together
and crystals grow
– Depends in part on which elements are present
– Temperature and pressure affect which minerals form
• Water with substances in it evaporates
– Salt water evaporates leaving halite (table salt)
– Gypsum often forms as water evaporates.
• Hot water within Earth’s crust moves through rocks and
dissolves minerals, then cools and the dissolved minerals
separate and become solid.
– Minerals can be moved from one place to another
• Gold that is dissolved can fill cracks in rocks when it becomes solid
again
• Minerals can form that are different from the ones that dissolved
– Lead from the mineral galena can become part of the mineral wulfenite
Minerals form in several ways.
• Minerals grow from magma which contains the types
of atoms found in minerals
– The atoms join together to form different minerals as
magma cools
– Minerals also form as lava cools.
• Quartz is one of the many minerals that crystallize from magma
and lava.
• Heat and pressure within Earth cause new minerals to
form
– Bonds between atoms break and join again.
• Garnet can grow and replace the minerals chlorite and quartz
– The element carbon is present in some rocks
• At high temperatures carbon forms the mineral graphite (pencil
lead)
• Organisms produce minerals.
– Ocean animals (oysters, clams) produce calcite and other
carbonate minerals to form shells.
– Your body produces apatite in your bones and teeth
Magma
Molten
rock
inside the
Earth
Both
Contains all types of
atoms that are
found in minerals
As magma cools,
different minerals
form
Lava
Molten rock
that reaches
Earth’s
surface
Minerals form in several ways.
Q. In what two ways can substances dissolved
in water eventually form minerals?
1. Water can evaporate leaving the substances
behind to crystallize into minerals.
2. The substances can be dissolved in hot
water, but can separate out when the water
cools.
Many minerals are mined.
• Minerals must be removed from the ground.
– Some are found near Earth’s surface
– Others lie deep underground
• Most are combined with other minerals in rocks
• Must be enough of the mineral present in a rock to be
worth mining
• Ores are rocks that contain enough mineral to be
mined for a profit
• Surface Mining recovers minerals at or near Earth’s
surface
– Some minerals are very dense and can build up in riverbeds
as less dense minerals are carried away
• In panning unwanted minerals that are less dense are washed away
• The gold and other dense minerals stay in the bottom of the pan
and can then be further separated.
• In bigger riverbed mining operations, miners use machines to dig
out and separate the valuable minerals.
Many minerals are mined.
• Strip mining occurs when miners strip away
plants, soil, and unwanted rocks from Earth’s
surface then use special machines to dig out an
ore.
• Open-pit mining involves removing the surface
layer of soil then useing explosives to break up
the underlying rock and recover the ore
• Roads are built up the sides of the pit to carry
ore to the surface.
– Copper and iron
Surface mining
In panning, a miner washes away some minerals, while
heavier minerals remain in the pan.
In strip mining, miners remove plants, soil, and unwanted
rocks, then use special machines to dig out the ore.
In open-pit mining, miners remove the surface layer of soil,
then use explosives to break up the rock and free the ore.
Deep mining
• Deep-mining methods are needed when an ore
lies far below Earth’s surface.
– Used to obtain many minerals.
• Miners dig an opening to reach deep ore
– From the main passage, miners blast, drill, cut, or dig
• Level passages are cut in hills or mountains to
reach ore
– Miners keep digging farther into the hill or mountain
• Vertical passages are cut to reach an ore that lies
underground in a flat area or under a mountain
– Ore is removed in layers