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Rocks & Minerals
NOTES
Pages 1 - 3
Key Concept #1
What is a mineral?
It is a
naturally occurring
substance which has a
inorganic
definite chemical composition
What would be the opposite of this?
man-made
organic
random composition
ESRT Mineral Chart Click Here
Are They Minerals???
Pearls
N
O
WHY???
They’re Made by a Clam or
Oyster
IT’S ORGANIC
Is it a Mineral?
WOOD?
WHY??
IT’S MADE FROM TREES
AND ORGANIC
ARE THEY MINERALS?
DIAMONDS
YES!!
WHY??
NOT MAN MADE
NATURALLY FOUND
PURE SUBSTANCE OF
UNIFORM
COMPOSITION
NOT ORGANIC
IS IT A MINERAL?
STEEL
NO!!!!
STEEL IS MAN MADE AND ISN’T
NATURALLY OCCURING
How Many Minerals are There??
T There are thousands of minerals but ONLY TWELVE
OF THEM ARE COMMON.
QUARTZ - Hardest common mineral
Key Concept #2
What causes minerals to have
different physical properties?
their internal arrangement of atoms
atom arrangements
Key Concept #2
Give an example of two minerals which have
the same chemical composition but different
physical properties Click Here
What causes the differences btn graphite and diamonds?
How Do Minerals Form?
Cooling Magma and Lava Mineral Crystals
Precipitation of minerals out of
Sea water – minerals in magma
are dissolved by water and as
the water cools the minerals
drop out of the water and sink
to the bottom
Key Concept #4
Minerals have a definite chemical composition.
What two elements, by mass, make up the greatest
percentage of the Earth’s crust?
oxygen
silicon
Key Concept #4
Minerals have a definite chemical composition.
These two elements combine to form MOST MINERALS
silicates (SiO4)- any mineral that has
silicon and oxygen in them
Key Concept #4
Minerals have a definite chemical composition.
They combine in a specific structure called a:
silicon-oxygen tetrahedra
Silicate Factory
Key Concept #3
The Main Physical Properties
Used to Identify Minerals
Color
a poor indicator
minerals can be
multiple colors
Ex: Quartz
Key Concept #3
The Main Physical Properties
Used to Identify Minerals
Streak
themore
powder
reliable
formthan
of a color
mineral
Pyrite and Gold
Pyrite – green black
streak
Gold
They have the same color but the streaks are
different. So streak can be more helpful than
color because two minerals may share the same
color but they can have different color streaks
Key Concept #3
The Main Physical Properties
Used to Identify Minerals
Hardness
resistance to being scratched
It is NOT the same as breaking!
For example:
You can break glass easily with steel.
However, steel will not scratch glass.
Key Concept #3
The Main Physical Properties
Used to Identify Minerals
Hardness
MOH’S SCALE OF HARDNESS
Hardness
Mineral
Hardness
Mineral
1 (softest)
TALC
6
ORTHOCLASE
2
GYPSUM
CALCITE
FLUORITE
7
QUARTZ
TOPAZ
CORUNDUM
APATITE
10 (hardest)
3
4
5
8
9
DIAMOND
Key Concept #3
The Main Physical Properties
Used to Identify Minerals
Luster
how light reflects off a mineral
metallic
1. Looks like a
Metal
2. Reflects most light off
the surface
3. USUALLY LEAVES A
DARK STREAK
non-metallic
1. Looks earthy,
waxy,
greasy or brilliant
2. Light is absorbed
or passes through
the mineral
Key Concept #3
The Main Physical Properties
Used to Identify Minerals
Cleavage
the mineral breaks in a predictable pattern
because of its arrangement of atoms
Key Concept #3
The Main Physical Properties
Used to Identify Minerals
Fracture
the mineral breaks randomly
Magnetism
Magnetite – common mineral that is magnetic
REACTION TO ACID
Reaction to Hydrochloric Acid – determines there is
calcium carbonate CaCO3 in the Mineral.
DOUBLE REFRACTION
AN IMAGE WILL APPEAR TO BE DOUBLED WHEN
LOOKING THROUGH A CLEAR CRYSTAL OF
CALCITE
CRYSTAL SHAPE
Shape of the geometric pattern
- Not always visible because the crystals do not
-
always have the space to grow; they bond to each
other and individual crystals are not visible.
Ex: Quartz individual crystals are hexagonal (6
sided)
Density
Density = Mass/Volume
**** THE BEST WAY TO IDENTIFY A MINERAL
BECAUSE THE DENSITY WILL NOT CHANGE WITH
THE SAMPLE SIZE AND WILL NOT BE AFFECTED BY
SMALL IMPURITIES.
EVERY MINERAL WILL HAVE IT’S OWN DENSITY
SPECIFIC GRAVITY
Comparison of the minerals density to the density of
water.
****If a mineral has a specific gravity of 4 then the
mineral is 4 times more dense than an equal
volume of water.