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Minerals
Section 4.1
Why Are Mineral’s
Important?
“Minerals play important roles in
forming rocks…and continue to play a
role in shaping civilization”
-Calcite is the mineral that forms the 2
million limestone blocks that make up
the Great Pyramid in Egypt.
-Wars have been fought and empires
have crumbled over minerals such s
gold and silver.
Quick History Lesson
• http://www.youtube.com/watch?v=rjhIzemLd
os
What is A Mineral? How are they
different from rocks?
• A mineral is a naturally
occurring, inorganic
solid with a specific
chemical composition
and a definite
crystalline structure.
• A rock is a naturally
occurring aggregate of
minerals
and/or mineraloids.
Rocks do not have a
definite chemical
composition.
• For example: Gabbro
has plagiocase,
pyroxene, olivine (all
minerals).
What Do You Mean Naturally
Occurring?
• It mean’s cannot be created in a lab. That
means synthetic diamonds that are created in
a lab cannot be minerals.
• Most natural diamonds are formed at high
temperature and pressure at depths of 140 to
190 kilometers (87 to 118 mi) in the Earth's
mantle.
Mineral Characteristics (Slide 1)
• All minerals are
naturally occurring by
natural processes.
Substances created in a
lab are not minerals.
• Second, all minerals are
inorganic. That is, they
aren’t alive and never
were during their
existence. (Let’s talk
about coal).
Coal Does Not Fit. Why?
• Coal is formed by ancient plants and animals
accumulating in moist peat bogs. As plants die off
in a wet area, they pile up into peat. It takes
between 4,000 and 100,000 years for one meter
of peat to accumulate. This process happens best
in river deltas or coastal plains.
• Over time, these peat seams are compressed by
further deposits and the carbon content of the
coal is concentrated. The older the coal gets,
generally, the harder and blacker it gets.
Mineral Characteristic’s (Slide 2)
Solid’s With Specific
Compositions
• -Solids have definite shapes,
gas and liquids do not.
• -Each type of mineral has a
chemical composition
unique to the mineral. Most
consists of a combination of
elements, while others (like
Silver) are composed of a
single element.
-Quartz
• A combination of two
oxygen atoms and one atom
of silicone.
Mineral Characteristics (Slide 3)
Definite Crystalline Structure
• The atoms in minerals are
arranged in geometric
patterns that are repeated
over and over again.
• Unfortunately, well defined
crystal shapes shown in the
examples are very rare.
Why? Most minerals are
formed in restricted spaces.
Crystal Systems
Important Mineral Groups To Know
• Silicates: Oxygen is the most abundant element in
earth’s crust, followed by silicon Minerals that
contain silicon and oxygen (and other elements)
are known as silicates. Examples are Quartz and
Feldspar.
• Carbonates: Carbonates are minerals composed
of one or more metallic elements with the
carbonate compound CO3
• Oxides: Oxides are compounds of oxygen and a
metal. Hematite (Fe2O3) and Magnetite (Fe3O4)
are examples of oxides.
Elements In Earth’s Crust
End of Section 4.1
Minerals
Section 4.2
Color
• Color is sometimes caused by
the presence of trace
elements or compounds
within a mineral.
• Quartz can be found in a
variety of colors because of
different trace elements. For
example purple amethyst
contains ferric iron.
• Color least reliable diagnostic
test. The same mineral can
have a variety of minerals,
have impurities, or be affected
by weathering.
Luster
• The way light reflects on
a mineral is called
luster. Luster is
described as metallic
and non-metallic. Silver,
gold, copper, etc have
shiny surfaces. Nonmetallic minerals, such
as calcite, gypsum, and
sulfur do not.
Texture
• Texture: Describes how
a mineral feels to touch.
Smooth, rough, ragged,
rusty, etc. This
diagnostic test is also
rarely used on it’s own
in the field.
Streak
• Streak: Is the color of a
mineral when it is
broken up and
powdered.
• For example, pyrite,
which is also known as
fool’s gold, leaves a
greenish back streak.
• A mineral’s streak is
rarely changed even
when it’s weathered.
Hardness
• Hardness: Is a measure of
how easily a mineral can
be scratched.
• For example, Talc is one
of the softest minerals
and can be scratched by a
fingernail.
• In contrast, diamond can
be used as a sharpener
and a cutting tool.
• Great diagnostic tool. Not
affected by weathering or
impurities.
Cleavage
• Cleavage: Minerals break
along planes where
atomic bonding is weak.
• Mica has perfect cleavage
that breaks long planes
where atomic bonding is
weak. Quartz breaks
unevenly among jagged
edges because of the
tightly bonded atoms.
Density and Specific Gravity
• Density is the mass of the
substance divided by the
volume.
• In the field, it is difficult
distinguish density
differences by lifting two
comparable minerals. That
is why we do a specific
gravity test.
• Specific Gravity is the ratio
of the weight of a substance
to the weight of an equal
volume at water at 4
(celcius)
Special Properties
• Some minerals have
unique special properties.
• Iceland Spar: Light is bent
in two different
directions. The refractions
creates the appearance of
two images.
• Calcite: Fizzes when it
comes into contact with
hydrochloric acid (HCl)
Mineral Identification Video
• http://www.youtube.com/watch?v=c7wJP_K_
sAQ
End of Chapter 4/ Final Question
• How can minerals be used for human use?
Give some examples.