Download Minerals-Wike

What is a mineral?
What are the characteristics of
all minerals?
1. A mineral occurs naturally.
2. A mineral is solid.
3. A mineral has a definite chemical
composition.
4. A mineral’s atoms are arranged in a
repeating pattern.
(What vocabulary term do you think of when you hear
this?)
5. A mineral is inorganic (was never
alive)
Is Coal a Mineral?
► We
burn coal as a source of energy. It
pollutes the air when burned.
► Is coal considered a mineral?
Is Coal a Mineral?
► Miners
refer to coal as a “mineral resource”
because it is removed from the ground.
Is Coal a Mineral?
► But
►
is it really a mineral?
(hint: look at the formation of coal and decide; keep the
characteristics of a mineral in mind)
Coal
► Coal
is referred to as a “mineral resource”
► Coal is not really a mineral because it formed from
once-living organisms
► Coal formed from swamp plants
► It takes millions of years for coal to form; this
makes it a nonrenewable resource
► Coal is a very important part of Virginia’s economy
► Coal is found predominantly in the Appalachian
Plateau physiographic province
Mineral Composition &
Groups
Of the almost 4000 known minerals,
only about 30 are common.
The most common are quartz,
feldspar, mica, and calcite.
Minerals
► Quartz
and feldspar are the 2 most
abundant rock-forming minerals in the
Earth’s crust
In fact, over 60% of the Earth’s
crust is made up of the family of
minerals known as feldspar!
These minerals make up most of
the rocks found in the Earth’s
crust.
Earth’s Crust
► Earth’s
crust is made up of 90 elements.
► 98% of the crust is made up of only 8
elements
Earth’s Crust
► The
eight most abundant elements in
Earth’s crust are as follows:
oxygen(O), silicon(Si), aluminum(Al),
iron(Fe), calcium(Ca), sodium(Na),
potassium(K), & magnesium(Mg)
Mineral Composition
► Minerals
are made up of elements found in
the Earth’s crust
► Minerals are in groups based on the
elements contained in them
Mineral Groups
► Major
groups of minerals are as follows:
1. Silicates 2. carbonates 3.oxides
4. sulfides 5. sulfates
6.halides
7. hydroxides 8. phosphates and
9. native elements
Silicates
► The
silicates are the largest group of rockforming minerals
► Silicates contain both silicon & oxygen and
one or more other elements
► Silicon and oxygen are the 2 most abundant
elements in the Earth’s crust
►
Pictured:Agate
To be able to identify these and
other minerals, we need to look at
the properties used to separate
and distinguish these minerals.
Identifying Minerals
Remember!:
Rarely is a mineral identified by a
single property.
These properties need to be
considered together to correctly
identify a mineral.
Physical Properties
►Color
►Luster
►Streak
►Hardness
►Specific
Gravity
Color is the most easily observed
mineral property and the least
useful!
Some exceptions to the color rule
would be cinnabar, which is always
red, sulfur, which is bright yellow,
and malachite, which is green.
Many minerals have a similar
color.
Many minerals can turn colors
due to impurities, or they can
change colors in various
circumstances.
For example, pure quartz is
colorless or white, impurities
can make the mineral rose,
purple or pink!
Discuss the following!
How many of the characteristics
of minerals can you name?
Why isn’t color a very good
property to identify most
minerals?
Luster refers to how light is
reflected from a mineral. Notice
the difference between these
two minerals.
The mineral on the left has a
metallic luster, and the one on
the right, a nonmetallic luster.
Terms used to describe nonmetallic
luster:
Dull, pearly, silky, glassy, and brilliant
Streak of a mineral is the color of its
powder when rubbed on a streak
plate or an unglazed porcelain tile.
The streak is often not the same
color as the mineral.
A minerals color may vary, but the
streak rarely will!
Streak
► For
example, both gold and pyrite look
alike. They appear to be the same thing.
► If you do the streak test, you will discover
that gold leaves a yellow streak, whereas
pyrite leaves a greenish-black or brownblack streak.
► Pyrite is known as “fool’s gold” because it
looks like gold, but is not
Gold & Pyrite
The cleavage of a mineral is its
tendency to split easily or to
separate along flat surfaces.
Cleavage can even be observed on
tiny mineral grains making it a very
useful property!
Mica is probably the best example as
it splits into thin sheets. It is said
to have one perfect cleavage.
Feldspar splits readily in two
directions, always at or near right
angles.
Calcite and galena cleave in three
directions.
They are said to have three good cleavages.
Not all minerals show cleavage.
Those that break with jagged edges are
said to have fracture.
Hardness of a mineral is how easily
the mineral can be scratched.
►Friedrich
Mohs devised a hardness
scale that we refer to as Mohs
Hardness Scale.
►In this scale, 10 well-known
minerals are given numbers from
1-10.
►Talc is the softest mineral and a
diamond is the hardest mineral
Mineral
Softness
Talc
1
Gypsum
2
Common
Objects
Hardness
Fingernail
2.5
Calcite
3
Penny
3.5
Flourite
4
Nail
4.5
Apatite
5
Glass
5.5
Feldspar
6
Steel File
6.5
Quartz
7
Streak
Plate
7
Topaz
8
Corundum
9
Diamond
10
► Common
objects are used to test the
hardness of minerals
ExampleCalcite has a hardness of 3 and a
copper penny just scratches it
because it has a hardness of 3.5
Example:
Apatite (left) has a hardness of 5 and can
be scratched by a steel knife blade.
Example
Quartz (left), with a hardness of 7, is
the hardest of the common minerals.
It easily scratches hard glass. Quartz
is also similar in composition to glass.
Gems are known for their extreme
hardness.
Crystal shape can be a useful
property to identify minerals if the
minerals have had the time and
space to form crystals. Most
mineral grains that are found in
rocks, lack the room to grow.
Specific gravity tells you how many
times as dense as water the
mineral is.
Pure gold can have a specific gravity
as high as 19.3!
Calcite is calcium carbonate, CaCO3.
If a drop of weak hydrochloric acid
is placed on calcite, the acid
bubbles as carbon dioxide is
released.
Magnetic
Malleable
Radioactive
Flourescence
Taste
Some minerals that
contain iron, are
magnetic and can
be picked up by a
magnet.
Magnetite is an
example of a
magnetic mineral.
This is the state of
glowing while
under a ultraviolet
light.
Some minerals even
glow once the light
is turned off!
Some minerals, such
as this uraninite,
are radioactive.
They give off
subatomic particles
that will activate a
Geiger counter.
Halite (rock salt)
can be identified
by its taste.
This practice is not
recommended!
Special Properties
Of Minerals
Special Properties
► Magnetite
is magnetic; lodestone is a type
of magnetite
► Calcite fizzes when you put hydrochloric
acid on it
► When you look through calcite, you can see
a double image
► Sulfur can be identified by its bright yellow
color and bad smell
2 Uses of Minerals
Gems
Ores
Gems
► Highly
prized because they are rare and beautiful
► Can be cut and polished and used for jewelry
► The brighter and more colorful samples are cut
and polished
► Example: amethyst- a form of quartz which has
manganese in it to give it its purple color
► Gems are very hard
Ores
►A
mineral that is Useful & Profitable
► Waste rock must be removed to get to the
desired mineral; removing waste rock is
very expensive.
► The value of a mineral can change if the
supply of or demand for that mineral
changes
Ores & Their Uses
► Examples:
► Bauxite-
aluminum
► Hematite- iron
► Galena- lead
► Halite- rock salt
► Graphite- pencil “leads
► Magnetite- iron