Identifying Minerals

Report
What is a mineral?
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Found in nature
Inorganic: not made from living things
Always in a solid form
Has a crystal structure
Definite Chemical composition: always has
the same elements is the same amount
Formation of Minerals
• Many minerals come from magma
•When magma cools mineral crystals are
formed.
• Magma that cools fast has small crystals
• Magma that cools slow has large crystals
•The two most abundant elements in the
earths crust are oxygen and silicon.
Minerals
• Each mineral has its own specific
properties that can be used to identify it.
• Learning these properties will make it easy
to identify minerals.
Hardness
• One of the best clues to use is hardness.
• Hardness is a mineral’s resistance to
being scratched.
• Mohs hardness scale – invented by
Friedrich Mohs in 1812
• Ranks 10 minerals from softest to hardest
Mohs hardness scale
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1 -Talc – softest known mineral. It
flakes easily when scratched by
fingernail.
2 – Gypsum – a fingernail can easily
scratch it.
3 – Calcite – A fingernail cannot
scratch it, but a copper penny can.
Mohs continued
• 4 – Fluorite – A steel knife can easily
scratch it.
• 5 –Apatite – A steel knife can scratch it.
• 6 – Feldspar – Cannot be scratched by
a steel knife, but it can scratch window
glass.
• 7 – Quartz – Can scratch steel and hard
glass easily.
Mohs continued
• 8 – Topaz – Can scratch quartz.
• 9 – Corundum – Can scratch topaz.
• 10 – Diamond – Hardest known mineral.
Diamond can scratch all other
substances.
Color
• Color is easy to identify
• Color can be used only to identify a few
minerals that always have their own
characteristic color.
• Azurite – always blue
• Malachite – always green
Streak
• The streak of a mineral is the color of its
powder.
• You rub the mineral against a streak plate
to see the powder.
• Pyrite – gold in color – black streak
• Gold – gold in color – golden yellow streak
Luster
• Luster is how the mineral reflects light
• Minerals with metals in them are often
shiny.
• Quartz is glassy.
• Other terms to describe luster are metallic,
waxy, pearly, earthy, and vitreous,
Density
• Each mineral has a characteristic density
• Density = the measure of how much
matter is in a given amount of space.
• No matter what size of the sample, the
density will always be the same.
• To find the density, measure the mass
with a balance and then put the sample in
water to find the volume. Use the formula
D = Mass/Volume (g/cm³) to calculate.
Cleavage
• Cleavage is the tendency of some
minerals to break along smooth, flat
surfaces.
• How the atoms in the crystal are arranged
will determine if the mineral has cleavage.
• Mica breaks easily into distinct sheets.
Fracture
• Most minerals do not split apart evenly.
• Fracture is the tendency of some minerals to
break unevenly along curved or irregular
surfaces.
• Quartz – shell-like shaped fracture, looks like
chipped glass
• Pure metals – form jagged points
Special properties
• Fluorite and Calcite are minerals that glow
under ultraviolet light
• Magnetite is a natural magnet that attracts
iron.
• Calcite will bubble or “fizz” when acid is
placed on it.
• Halite taste salty
• Minerals that contain radium and uranium
are radioactive.
Mining Minerals
An ore is a mineral deposit large enough and pure
enough to be mined for profit.
Mining
1. Strip mining – earthmoving equipment
scrapes away soil to expose ore
2. Open-pit – miners use giant earthmoving
equipment to dig a tremendous pit
3. Shaft mining – network of tunnels that
extend deep into the ground.
Reclamation
Mining can be harmful to the environment.
Reclamation – process by which land used for
mining is returned to its original state or better.
Another way to reduce the effects of mining is
to reduce our need for minerals - recycling
Essential Questions
Please answer in complete sentences
• What properties can you use to determine the
type of mineral?
• Describe how you can test a mineral to
determine its hardness, density, and streak.
• How are cleavage and fracture similar? How
are they different?
• Explain why you can’t rely on any single test or
property when you are trying to identify a
mineral.

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