Minerals
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Mineral Definition
Most Abundant Elements
Classification of Minerals
Mineral Identification
Mineral
A Naturally Occurring
Inorganic Solid
with a Definite Chemical
Composition
and Crystalline Structure.
A. Naturally occurring
A mineral has to be
found on the earth's
surface or dug up out
of the crust, not made
in a lab somewhere by
people.
Examples of manmade objects are
bricks, cement,
and glass
B. Inorganic
This means that they
do not come from
living things.
Since coal forms naturally in the crust
and from living things it is not a mineral
C. Solid
Solids are substances
that have a definite
shape and a definite
volume.
The particles are
tightly packed and
can not flow freely.
D. Crystal structure
The atoms that
minerals are made of
are connected to
each other in a
pattern.
This pattern is called
its crystal structure.
The flat sides form
faces
E. Definite Chemical Composition
This means that there is a
specific chemical formula
for each mineral.
The mineral pyrite is made
of 1 atom of iron for every
2 atoms of sulfur. (FeS2)
Pyrite will have the same
chemical formula
regardless of where it is
found.
How Minerals Form
Crystals from Magma
Magma cools = atoms bunch
together/combine
• Cools fast = small crystals
• Cools slowly = larger crystals
•
Crystals from Solution
Water evaporates (leaving behind ions that
form into crystals)
• Halite
•
How do minerals
form?
In general minerals can form in two ways:
through crystallization of melted
materials, and through crystallization of
materials dissolved in water.
Magma that cools at a slow rate will
produce large crystals while magma or
lava that cools rapidly will produce small
crystals.
Most Abundant Elements in the Earth’s Crust
Aluminum
8%
Iron
5%
Calcium 4%
Sodium 3%
Silicon
27%
Oxygen
46%
Potassium 3%
Magnesium
2%
Other
2%
Silicates (SiO4)
Quartz (SiO2)
Agate - Onyx (SiO2)
Amethyst (SiO2)
Beryl - Aquamarine (Be3Al2(SiO3)6
Chalcedony (SiO2)
Orthoclase (K, Al Si3O8)
Plagioclase (Na, Ca, Al3SiO4)
Nepheline (Na, Ca, AlSiO2)
Muscovite - mica (K, Al3 Si3O10)
Biotite - mica (K, (Mg, Fe)3 Al3SiO10)
Olivine (Mg Fe)2 SiO4)
Pyroxene (Mg, Fe)2, Ca, Al SiO4)
Amphibole - Hornblende (Mg, Fe Ca Al SiO4)
Garnet (Mn, Mg, Fe, Ca, SiO4 )
Talc (Mg3Si4O10)
Carbonates
(CO3)
Calcite (CaCO3)
Dolomite (Ca, Mg, CO3)
Siderite (FeCO3)
Cerussite (PbCO3)
Malachite (CuCO3)
Sulfates (SO4)
Gypsum (CaSO4)
• alabaster
• satin
spar
• selenite
Halides
Halite (NaCl)
Fluorite (CaF2)
Iron Oxides FeO
Magnetite (Fe3O4)
Hematite (Fe2O3)
Goethite (HFeO2)
Chromite (FeCr2O4)
Limonite (2 FeO)
Sulfides
Pyrite (FeS)
Galena (PbS)
S
Oxides
Corundum (Al2O3)
Phosphates (PO4)
Apatite Ca5(OH, F, Cl)(PO4)3
Native Elements
Gold Au
Silver Ag
Copper Cu
Sulfur S
Graphite C
Diamond C
Mineral Identification
Identifying
Minerals
Each mineral has its own
characteristics or properties
that help you identify it.
The Physical Properties of Minerals
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Hardness
Color
Streak
Luster
Fracture
Cleavage
Specific Gravity
Other – magnetic, smell, taste, acid
Mohs Scale
1824, Freidrich Mohs
Mohs Scale of Hardness
1 Talc
2 Gypsum
3 Calcite
4 Fluorite
5 Apatite
6 Orthoclase (Feldspar)
7 Quartz
8 Topaz (Beryl)
9 Corundum
10 Diamond
Moh’s Scale of Hardness
Ticking
Generally
Continues
From
An
Old
Quartz
Timex
Calendar
Display
Hardness #1
Talc - talc
has perfect cleavage in one direction. This means that
this mineral breaks into thin sheets. As a result, it feels greasy to the
touch (which is why talc is used as a lubricant).
Hardness #2
Fingernail 2.5
Gypsum
Shape: Monoclinic (often forms thick tabular or prism
shaped crystals)
Luster: Pearly
Color: White, yellowish, or brown
Streak: White
Hardness: 2 on Mohs Hardness Scale
Cleavage: Perfect in one direction, poor in another direction
Fracture: Thin elongate fractures
Hardness #3
Piece of copper (2.5-3)
Calcite
Shape: Trigonal
(rhombahedral shape)
Luster: Glassy to resinous.
Large samples often look dull.
Color: Usually white or
colorless but sometimes is
found in light pastel colors.
Streak: White
Hardness: 2.5 to 3
Cleavage: Perfect in three
directions
Fracture: Conchoidal
Everyone's favorite way of identifying calcite is the acid test. When you
place a drop of weak acid, such as vinegar, on calcite, it will bubble. This
happens because a reaction causes a little bit of the calcite to break down,
releasing carbon dioxide gas, making the bubbles.
Hardness #4
Iron nail 4.5
Fluorite
Hardness #5
Glass 5.5
Apatite
Hardness #6
Feldspar
Shape: Monoclinic (Flat
tabular or prismshaped crystals)
Luster: Glassy or pearly
Color: Cream to pink
Streak: White
Hardness: 6
Cleavage: Yes
Fracture: Conchoidal
or brittle
Hardness #7
Quartz
Shape: Trigonal (Perfect crystals
are usually 6-sided prisms with
a pyramid shape at the end.
However, it is much more
common to find many crystals
that have grown in a mass or
broken crystals.)
Luster: Glassy or greasy
Color: Colorless or white. Some
varieties are pink or smoky.
Streak: White
Hardness: 7 on Mohs Hardness
Scale
Cleavage: None
Hardness #7
Quartz
These three crystals of the mineral quartz show how the same type of mineral can
have different colors! The pink sample is called rose quartz and the dark sample is
called smoky quartz. Notice how these samples do not look like crystal shapes
because they have fractured.
Windows to the Universe
Hardness #8
Hardness #9
Corundum
Hardness #10
Luster
Descriptions of Luster
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Metallic
Glassy
Earthy
Dull
Waxy
Vitreous (clear)
Silky
Pearly
Resinous (plastic)
Sub-metallic
Greasy
Specific Gravity
Ratio of weight of the mineral when
compared to the same volume of water.
Streak
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The color of a mineral when it is in
powder form
Mineral must be softer than streak plate
Cleavage and Fracture
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The way a mineral breaks
Cleavage – mineral can be broken along
smooth, flat plains
Fracture – minerals that break with
uneven, rough, or jagged surfaces
Other Properties
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Magnetic
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Acid Test
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