Download Minerals

Minerals
What is a Mineral?
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Naturally Occurring
Inorganic
Solid
Definite Chemical Formula
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Definite Crystal Structure
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Naturally Occurring
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Formed by natural processes not in the
laboratory.
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Is an ice cube a mineral?
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Is the ice on the windshield of a car a mineral?
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Minerals manufactured by humans are not
considered minerals.
Inorganic
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Formed by inorganic processes; not living
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Minerals are not made from living things.
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Coal is made of carbon. Is it a mineral?
Solid
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Minerals cannot be a gas or a liquid.
- H2O as ice in a glacier is a mineral, but
water is not.
Definite Crystal Structure
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Highly ordered atomic arrangement of
atoms in regular geometric patterns
Minerals are crystals with a repeated inner
structure.
Apatite
Feldspar
Diamond
Quartz
Definite Chemical Formula
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Minerals are
expressed by a
specific chemical
formula.
Minerals made of only
one type of atom
(element) are called
native elements.
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Gold (Au)
Calcite (CaCO3)
Quartz (SiO2)
Pyrite
(FeS2)
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Gold
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Copper
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Silver
Types of minerals
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Minerals are most commonly classified by
chemical composition.
The 2 main groups are silicates and
nonsilicates.
Silicates
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Minerals containing a combination of silicon (Si)
and oxygen (O) (most common elements in the
earth’s crust)
Silicate minerals comprise about 90% of the
Earth’s crust.
Silicates minerals often contain other elements
such as aluminum, iron, magnesium, and
potassium.
Granite is a rock comprised of the minerals
feldspar, biotite mica and quartz.
Feldspar
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Feldspar minerals make up
half of the Earth’s crust and is
the main component of most
of the rocks found on the
Earth’s surface.
Feldspar contains Si, O, Al, K,
Na, and Ca
Feldspar
Biotite Mica
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Soft and shiny
minerals that separate
easily into sheets
Biotite is one variety
of mica
Quartz
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Silicon dioxide ( SiO2)
is the basic building
block of many rocks
Nonsilicates
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Minerals that do not contain the
combination of Si and O
Some of these minerals are made up of C,
O, F, and S
Classes of Nonsilicates
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Native Elements
Carbonates
Halides
Oxides
Sulfates
Sulfides
Native Elements
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Native elements are
composed of only 1
element
About 20 exist
including Au, Pt, C,
Cu, S and Ag
Carbonates
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Contain the
combinations of carbon
and Oxygen in their
chemical structure
Calcite (CaCO3 ) is an
example
Carbonates are used in
cement, building stones
and fireworks
Halides
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Form when atoms containing
fluorine, chlorine, iodine, or
bromine (halogens) combine
with potassium or calcium
Halite (NaCl) is better known
as rock salt
Fluorite can have many
different colors
Halides are often used in
making fertilizers
Fluorite
Oxides
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Compounds formed
when elements like
aluminum or iron bond
with oxygen
Corundum (Al2O3) and
Magnetite (Fe3O4) are
important oxides
Are used in abrasives
and airplane parts
Sulfates
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Minerals containing sulfur
and oxygen (SO4)
Gypsum (CaSO4 * 2H2O) is a
common example
makes the white sand at
White Sands National
Monument in NM
Sulfates are commonly used
in cosmetics, toothpaste and
paints
Gypsum
Sulfides
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Minerals containing one
or more elements such
as lead, iron, or nickel
combines with sulfur
Galena (PbS) is a
sulfide
Sulfides are used to
make batteries,
medicines and
electronic parts
Galena
Composition of the Earth’s Crust
 Eight Elements that make up over 98% of
Earth’s Crust
-
Oxygen (O)
Silicon (Si)
Aluminum (Al)
Iron (Fe)
Calcium (Ca)
Sodium (Na)
Potassium (K)
Magnesium (Mg)
Where Do Minerals Come From?
In general, minerals form in two ways:
Cooling magma - Crystallization of melted materials
From solution - Crystallization of materials dissolved in water
Magma
a. At the surface
b. Beneath the
surface
Evaporation
Magma
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Magma is molten material from the mantle
that hardens to form rock.
Lava is magma that reaches the surface.
Minerals form as hot magma cools inside
the crust, or as lava hardens on the
surface.
When these liquids cool to the solid state,
they form crystals.
Size of Crystals
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Depends of several factors:
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The rate at which the magma cools
The amount of gas the magma contains
The chemical composition of the magma
When magma remains deep below the
surface, it cools slowly over many
thousands of years.
Slow cooling leads to the formation of
large crystals.
Magma closer to the surface cools much
faster, producing smaller crystals.
Minerals from Hot Water Solutions
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Sometimes, the elements that form a mineral
dissolve in hot water and form a solution.
A solution is a mixture in which one substance
dissolves in another.
When a hot water solution begins to cool, the
elements and compounds leave the solution and
crystallize as minerals.
This can happen on
the ocean floor when
ocean water seeps
down through cracks
in the crust.
Minerals formed by Evaporation
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Minerals can also form when solutions
evaporate. Example: salt from sea water
Several other useful minerals also from by
the evaporation of seawater:
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Gypsum
Calcite crystals
Minerals containing potassium
Minerals formed by Metamorphism
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When rocks are put under extreme heat
and pressure, the chemical composition of
the rock can change, forming new
minerals.
Examples: calcite, garnet, graphite,
hematite, magnetite, mica and talc.
How Are Minerals Identified?
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Color
Luster
Hardness
Streak
Density
Crystal Shape
Cleavage and Fracture
Special Properties
Color
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Usually the first and most easily observed
Not a reliable way to identify a mineral
- Some minerals are the same color as others
- Some minerals can have many colors
ROSE QUARTZ
QUARTZ
SMOKY QUARTZ
Luster
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General appearance of a mineral surface in
reflected light
Glassy-Obsidian
Examples of luster
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Metallic
Vitreous: similar to glass
Resinous: resembles the way plastic reflects light
Pearly: resembles the way pearls shine
Greasy: resembles the way petroleum jelly or a greasy
surface reflects light
Silky: resembles the way silk reflects light
Earthy: dull, may be rough or dusty
Waxy
Adamantine: resembles the way a diamond shines
Fibrous – looks like fibers
Pitchy – looks like tar
Hardness
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Resistance to scratching by different items;
“scratchability”
Mohs Hardness Scale is used to determine the
hardness of minerals by comparing them to
substances of known hardness.
Mohs Mineral Hardness Scale
1) Talc
Softest
2) Gypsum
3) Calcite
1
5
4) Fluorite
5) Apatite
9
2
6) Feldspar
6
7) Quartz
8) Topaz
3
7
9) Corundum
10) Diamond
10
Hardest
4
8
Streak
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The color of a finely powdered mineral
Determined by rubbing the mineral on a piece
of unglazed porcelain (streak plate)
Density
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The amount of matter in a given space
Specific Gravity is the comparison of a substance’s
density to the density of water
Crystal Shape
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Minerals have a
characteristic crystal
shape resulting from the
atomic packing of the
atoms when the mineral
is forming
Cleavage and Fracture
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Cleavage is the tendency of a mineral
to split or crack along parallel or flat
planes.
Fracture occurs when a mineral breaks
at random lines instead of at consistent
cleavage planes.
BIOTITE
1 Direction of Cleavage
QUARTZ
No Cleavage
Obsidian
Conchoidal Fracture
Fracture
Special Properties
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Magnetism (Magnetite)
Glowing under ultraviolet light (Fluorite)
Taste (Halite)
Smell (Sulfur)
Reaction to HCl (Calcite)
Double refractive - a thin, clear piece of
calcite placed over an image will cause a
double image
Radioactivity - minerals containing radium or uranium
can be detected by a Geiger counter
Economic Importance of Minerals
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Minerals are in many things we see and
use everyday such as; bricks, glass,
cement, plaster, iron, gold
Every American Requires 40,000
Pounds of New Minerals per Year
At this level of consumption the average newborn infant will
need a lifetime supply of:
- 795 lbs of lead (car batteries, electric components)
- 757 lbs of zinc (to make brass, rubber, paints)
- 1500 lbs of copper (electrical motors, wirings
- 3593 lbs aluminum (soda cans, aircraft)
- 32,700 lbs of iron (kitchen utensils, automobiles, buildings)
- 28,213 lbs of salt (cooking, detergents)
- 1,238,101 lbs of stone, sand, gravel, cement (roads, homes)