Download Minerals

All the rocks and minerals in the Earth’s lithosphere are
made of elements, but not all rocks are minerals.
To be classified as a mineral it must be:
1. A solid
2. Naturally occurring
3. Inorganic
4. Have a crystal structure
5. Has a definite chemical composition.
There about 4000 known minerals, however of all the
elements in the Earth’s crust, only a mere eight make-up
98.5% of the crust total mass. Of those eight elements,
more 90% of the minerals are compounds containing
only two.
Oxygen – 46.6%
2. Silicon –
27.7%
3. Aluminum – 8.1%
4. Iron –
5%
1.
5. Calcium
–
3.6%
6. Sodium –
2.8%
7. Potassium – 2.6%
8. Magnesium – 2.1%
The formation of minerals is a process known as
crystallization.
There are three main ways minerals crystallize:
Magma Process
2. The Pressure Process
3. Crystallization from solution
1.
Convection currents deep in the Earth’s mantle
cause magma to rise and begin to cool. As the
magma cools, atoms, molecules, and ions arrange
themselves into regular, repeating patterns and
bond forming various crystals.
Pressure chemically breaks down the rock
2. Heat and pressure change the rock’s properties
without melting the rock
3. The atoms, ions, and molecules recombine to
form new minerals
1.
When water cools or evaporates, the particles of
dissolved minerals come together again and crystallize.
Every mineral has a unique set of physical properties
that are used to identify it. These properties include:
1.
2.
3.
4.
5.
6.
7.
8.
Color
Luster
Hardness
Streak
Cleavage
Fracture
Density
Specific Gravity
Color is the easiest of all properties to observe however,
it is the least reliable.
Luster describes the way a mineral surface reflects
light. Lusters include:
1.
2.
3.
4.
5.
6.
7.
Metallic
Nonmetallic
Greasy
Dull
Earthy
Glassy
Pearly
Hardness is a mineral’s resistance to being scratched.
Mineralogist Friedrich Mohs devised a numeric scale to
determine the hardness of a mineral.
The streak of a mineral is the color of its powder. Streak
is obtained by rubbing the mineral on a streak plate.
Cleavage is a mineral’s tendency to split along smooth,
flat surfaces.
Fracture occurs when a mineral breaks along rough or
irregular surfaces.
Special type of fracture that occurs in glassy type
minerals.
Many minerals have similar densities however, very high
or low densities can be used to identify certain minerals.
Examples: Pumice: .64 g/cm3
Platinum: 21.5 g/cm3
Formula:
A mineral’s specific gravity is the ratio of its dry mass to
the mass of an equal volume of pure water. In general,
the specific gravity of a mineral tells you how many
times denser the mineral is than pure water.
Formula:
Specific Gravity = ______Dry Mass______
(Dry Mass) – (Wet Mass)
Some minerals have unusual characteristics that can be
used to identify specific minerals.
Double Refraction occurs when a single light wave is
split into two.
Example: Iceland spar
When certain minerals are exposed to ultraviolet light
they will glow.
Minerals such as calcite and halite have a salty taste.
Minerals such as lodestone and magnetite are naturally
magnetic.
Some minerals such as carnotite and uraninite give off
radiation that can be detected using a Geiger Counter.
Minerals are classified according to similarities in
composition. Minerals are classified into four main
groups:
Silicates
2. Carbonates
3. Oxides
4. Sulfides
1.
Silicates are any minerals that contain silicon and
oxygen. The basic building block of a silicate is the
silica tetrahedron.
Properties
Quartz
SiO2
Color
Colorless, rose,
amethyst, smoky
Luster
Glassy
Hardness
7
Streak
White
Break
Conchoidal
Density
Specific Gravity
1.2 g/cm3
2.65
Crystal Structure
Silica Tetrahedron
Special Properties
-
The feldspar family makes up approximately 60% of
Earth’s crust
The molecular difference between quartz and feldspar is
that the silicone atom is replaced by either an aluminum,
potassium, sodium, or calcium atom. Feldspar is
classified into two main groups:
Orthoclase Feldspar: Potassium atom
2. Plagioclase Feldspar: Sodium-calcium atoms
1.
Properties
Orthoclase Feldspar
Plagioclase Feldspar
Color
Salmon with parallel white
fibers
White to gray
Streak
White
White
6
6
Pearly
Pearly
Silica Tetrahedron
Silica Tetrahedron
Cleavage (two directions)
Cleavage (two directions)
Density
2.55-2.75
2.55-2.75
Specific Gravity
2.5 – 2.6
2.5 – 2.6
Hardness
Luster
Crystalline
Structure
Break
Orthoclase Feldspar
Plagioclase Feldspar
Pyroxene Family: Ferromagnesian
Properties
Augite
(Ca,Na)(Mg,Fe,Al)(Al,Si)2O6
Color
Brownish green
Luster
Glassy
Hardness
5 – 6.5
Streak
Greenish gray
Break
Cleavage
Density
1.2 g/cm3
Specific Gravity
2.65
Crystal Structure
Silica Tetrahedron
Special Properties
-
Mineral in the mica family are soft silicates:
Muscovite and Biotite are minerals that form flat crystals
that cleave in only one direction to form thin sheets.
A carbonate is a mineral made of negatively charged
carbonate ions bonded to a positive metal ion. Each
carbonate is composed of 1 carbon atom and 3 covalently
bonded oxygen atoms.
Properties
Calcite
CaO3
Color
Colorless/White
Luster
Glassy
Hardness
3 – 3.5
Streak
White
Break
Cleavage
Density
2.7 g/cm3
Specific Gravity
2.7
Crystal Structure
Rhombohedra
Special Properties
Fluorescent
Acid Test
Bubbles
Properties
Dolomite
CaMg(CO3)
Color
White
Luster
Glassy
Hardness
3.5 - 4
Streak
White
Break
Cleavage
Density
2.48g/cm3
Specific Gravity
2.8
Crystal Structure
Rhombohedra
Special Properties
-
Oxides are any mineral containing significant amounts
of iron and oxygen.
Sulfides are any mineral containing significant amounts
of iron and sulfur.
Oxides and sulfides are used in manufacturing to make
steel, medicines, cosmetics, plastics, and paints.
Any mineral that can be sold for a profit is known as an
ore.
Properties
Hematite
Fe2O3
Magnetite
Fe3O4
Pyrite
FeS2
Color
Black, Red
Black, Brown, Gray
Pale to Bright
Yellow
Luster
Metallic, Earthy
Metallic
Metallic
Hardness
5-6
5.5 – 6.5
6 – 6.5
Streak
Red
Black
Greenish Black
Break
Fracture
Fracture
Conchoidal
5.255 g/cm3
5.175 g/cm3
4.9 g/cm3
5.3
5
5
Crystal Structure
Hexagonal
Octahedral
Cubic
Special Properties
-
Magnetic
-
Density
Specific Gravity
Hematite
Magnetite
Pyrite