Download Mineral Resources

Mineral resources
Mineral resources are:
• Minerals or rocks mined from the earth
and used in the products we use daily.
• Coal, oil, and natural gas are also mined,
but these energy resources will be
considered separately.
The use of minerals and rocks in products
• Sometimes actual minerals and rocks are used in
products or to make things. The rock granite is mined
to make countertops, and the mineral halite is mined,
crushed, and sold as table salt.
• Other times, minerals and brines are processed to
extract one specific element, and these individual
elements are often called mineral commodities. For
example, the commodity aluminum is extracted from
the rock bauxite, which contains aluminum-bearing
minerals like gibbsite.
• The process of extracting the desired mineral or
element from an ore is called beneficiation.
Minerals
Minerals are:
• solid
• inorganic (or identical to an inorganic mineral)
• natural (or made in a way that mimics nature)
• chemically homogeneous (that is, the mineral contains the same
chemicals throughout)
• crystalline (the atoms in a mineral are arranged in an orderly
and repeating pattern)
Examples of minerals
Mineral
Chemical
formula
Quartz
SiO2
Elements in
Si = silicon, O =
these minerals oxygen
(two oxygen
atoms for every
one silicon atom)
Hematite
Fe2O3
Diamond
C
Fe = iron, O =
C = carbon
oxygen (two iron
atoms for every
three oxygen
atoms)
Halite
NaCl
Na = sodium,
Cl =
chlorine
Crystal
structures
Na
Si
O
Fe
O
C
Cl
NOT minerals
The "minerals" in these “vitamins and minerals” are not
real minerals. These are elements that may have been
extracted from minerals.
Common elements and common minerals
• Minerals are comprised of elements.
• Eight elements make up the majority of Earth's crust and
mantle:
What’s within the crust (by mass)
Elements in the crust
Mass%
Oxygen (o)
46.6%
Silicon (Si)
27.72%
Aluminum (Al)
8.13%
Iron (Fe)
5.00%
Calcium (Ca)
3.63%
Sodium (Na)
2.83%
Potassium (K)
2.59%
Magnesium (Mg)
2.09%
All others
Common metals
(Al,Fe,Ca,
Na, K,
Mg)
Oxygen
Silicon
Common elements and common minerals
• These elements can combine in a variety of ways to make different
minerals.
• Most minerals contain silicon and oxygen (plus other elements).
These minerals are called silicate minerals.
Crystal structure of almandine
garnet (Fe3 Al2 Si3 O12 )
containing iron and aluminum in
addition to silicon and oxygen.
Fe
Al
Si
O
Common elements and common minerals
Why do we care about this?
• Sustainability: The eight elements just listed are the most
plentiful. Other elements are more rare; we find them less
frequently and have a lower overall supply of them.
• Ease of use: Silicate minerals tend to be refractory; they have
high melting points and low solubilities, so they hold onto the
elements within them.
• Although the majority of Earth’s elements are found in silicate
minerals, they are usually found in higher quantities in nonsilicate
minerals, commonly oxide or sulfide minerals. It is more efficient
to mine elements when they are found in higher concentrations.
If we want the element in the mineral (and not the mineral itself), then
we seek nonsilicate minerals that contain the element, because it is
easier (fewer resources are needed) to extract those elements from the
mineral. For example, although the silicate mineral fayalite (Fe2SiO4)
contains iron (Fe), it is easier and more efficient to extract iron from
hematite (Fe2O3), which is a nonsilicate mineral.
Fayalite. Not an economic source for
iron, though it contains iron.
Hematite. Iron is commonly extracted
from this mineral.
Mineral properties
• A mineral's chemical and
crystalline nature gives it
properties that make it
useful.
• These properties also must
be considered when
determining how best to
mine, process, and dispose
of the mineral and mine
waste.
Mineral properties: Chemistry
• The elements within minerals give them
distinct and useful properties.
For example:
Sulfur allows gunpowder to ignite at a
lower temperature and provides fuel for
the fire.
Sulfur can be found as
a mineral (native sulfur,
S)
Sulfur can also exist
as an element within
other minerals like
pyrite (FeS).
Mineral properties: Chemistry
For example:
Aluminum metal is very
lightweight but strong.
Aluminum does not form a mineral on its
own, but is beneficiated from the minerals
gibbsite and bohemite.
Aluminum alloys were extensively
used for constructing Apollo 16 whose
Command and Service Module (CSM)
"Casper" is shown here
Mineral properties: Hardness
A mineral's hardness is determined by:
– The crystalline nature of that mineral,
– The type and strength of bonds that hold the atoms
together, and,
– The nature of the repeating pattern
Crystal structure
for graphite
Both graphite and
diamond are made up of
the same element, carbon
(C). However, diamond is
much harder than
graphite.
Crystal structure
for diamond
Carbon
Carbon
Mineral properties: Hardness
For example:
Very hard minerals (like diamond, corundum, and garnet) are
useful as abrasives. Saw blades impregnated with diamonds can cut
rock, and sandpaper is often made with garnet sand.
Almandine garnet crystals. Hardness
of almandine garnet is 7–8
On the Moh’s scale of hardness
Talc (hardness = 1 on the Moh’s scale of
hardness) is used in baby powder because it
is a very soft mineral.
Mineral properties: Color
Some minerals have distinct, and vibrant, colors. This
makes them incredibly useful as pigments in paints,
cosmetics, colored plastic, etc.
The rust red color of
hematite (left) and
rust yellow color of
limonite ( a variety
of goethite, right)
have long been used
as a pigment.
Malachite’s green
color has made it
useful in paints
Mineral properties: Color
For example: The native people in Himba Village, Namibia, powder
iron oxide minerals (like hematite and goethite) to color their skin and
hair.
Mineral properties: Specific gravity
Specific gravity is a relative density, determined both by a
mineral's chemistry (minerals containing heavier elements will
have higher specific gravities) and how closely together the
atoms are packed.
Galena (PbS) contains the heavy
element lead, giving it a high
specific gravity
Mineral properties: Behavior of light in the crystal
The crystalline structure determines if and how light passes through a
mineral. For example, light reflects inside of diamond, which gives
diamond ring an exquisite sparkle.
Other minerals (like rutile) are quite opaque, which makes titanium
oxide (the chemical name of rutile) an important additive in things that
need to be opaque, like paint.
Some minerals are also useful in blocking other wavelengths of light;
barite and lead (from the mineral galena) block X-rays, for example.
The crystalline structure of calcite (Iceland spar
variety) can split light rays passing through it,
making the horizontal lines seen through the
calcite crystal appear to double up in this photo.
Iceland Spar crystals were once used in
polarizing microscopes and telescopes because of
this property.
Mineral properties: Luster
Luster describes how light interacts with the surface of a mineral.
For example, the mineral hematite can have both metallic or
nonmetallic luster; hematite with metallic luster (photo on left) is
used to make jewelry.
Mineral properties: Crystal shape and cleavage
These are determined by the nature of the crystalline
structure. The sheet-like cleavage of muscovite allows
it to be broken into tiny pieces of glitter.
Muscovite’s cleavage causes it to break into sheets.
Mineral properties: Solubility
Different minerals dissolve differently depending on
their crystalline structure (the type of bonds) and
chemistry. When a mineral dissolves, it breaks into the
ions that it contains.
Some dissolve quickly in water (or acidic or alkali
solutions), whereas others are very stable.
For example, people eat tablets
made of calcite; that calcite
dissolves in the stomach,
neutralizing some of the acid
and reducing heartburn
TUMS® tablet dissolving in acidic water
releasing bubbles of carbon dioxide.
Mineral properties: Solubility
For some applications, an insoluble mineral is preferred.
For example, the Eads Bridge that crosses the
Mississippi River is faced with rock made of insoluble
minerals below the water line, whereas more decorative
limestone (made of the more soluble mineral calcite)
faces the support above the water line.
If a mineral is being mined from the element it contains,
then it will be easier to extract that element from a
soluble mineral.
Mineral properties: Magnetism
The chemistry of certain minerals allows them to
store an applied magnetic field. For example,
magnetic minerals in a hard drive can be programmed
to store information.
A bar magnet hanging from a sample
of magnetite. Magnetite is an iron
oxide (Fe3O4), and is naturally
magnetic.
Mineral properties: Electrical conductivity
Electrical conductivity is mainly
determined by the presence of metallic
bonds. Metals have these bonds, which is
why metals are favored for wires.
Copper’s electrical conductivity
and resistance to corrosion make it
ideal for electric wiring.
Copper can be found as a pure
metal (native copper, Cu)
Copper is often
beneficiated from
minerals like
chalcopyrite
(CuFeS2).
Mineral properties: Electrical conductivity
Minerals that have low electric conductivity will be used
for insulators, which block and/or confine the electric
current.
Clay minerals such as kaolinite show
very low electrical and thermal
conductivity.
Ceramic insulators made from clay
minerals are used for supporting
electric power lines
Mineral properties: Thermal conductivity
Minerals can also be used to conduct or confine heat.
Thermal conductivity is determined by both a
mineral’s chemistry and crystalline structure
Clay minerals such as kaolinite show
very low electrical and thermal
conductivity.
Ceramic kitchen utensils made from
clay minerals are used to confine the
temperature of food and beverages
Mineral properties: Melting point
Different minerals melt at different temperatures.
Minerals with high melting points are used for hightemperature applications.
For example, the mineral graphite
is used for lining furnaces and as
crucibles for melting metals
Mineral properties: Response to stress
Different minerals/rocks behave differently under stress.
For example, while many minerals will shatter if hit with
a hammer, gold is malleable. This allowed early people to
easily shape it into ornaments.
Piezoelectricity is another property related to
stress. An electric current is generated in
piezoelectric minerals when a stress is applied.
For example, a hammer hits a piezoelectric
crystal, and this will generate a spark to ignite a
cigarette lighter. The piezoelectricity of quartz
allows it to be used to tell time (in quartz crystal
watches), and piezoelectricity is also useful in
transformers and motors.