Minerals
CH 2 Prentice Hall
p. 47-54
What is a Mineral?
• A naturally occurring,
inorganic solid that has
a crystal structure and
definite chemical
composition.
– Over 3,000
– 20 minerals form
Earth’s crust.
• Rock forming minerals.
Naturally Occurring
• Must form through
Earth’s processes.
– Cement, Brick, Steel
and Glass all come
from substances in
Earth’s crust.
– But they are
manufactured by
people.
Inorganic
• Cannot come from
materials that were once
part of living things.
– Coal- forms naturally,
comes from the remains
of plants and animals.
Solid
• Always solid, with a
definite volume and
shape.
– Particles can’t flow
freely.
Crystal Structure
• Particles of a mineral line up in a repeating
pattern. Forms a solid called a crystal.
– Has flat sides called faces, that meet at sharp
edges and corners.
Definite Chemical Composition
• A mineral always contains certain elements in
definite proportions.
• Element- a substance composed of a single
kind of atom.
– All atoms have the same chemical and physical
properties.
Definite Chemical Composition
• Compound- Two or more elements combined.
– Most minerals are compounds.
– Chemically joined.
Definite Chemical Composition
• Mixture- consists of two or more substances
that are mixed together but not chemically
combined.
Crystal Structure
• Each mineral grows atom to atom to form that
mineral’s particular structure.
– Classified into six groups (crystal systems) based
on the number and angle of the crystal faces.
Identifying
Minerals
Identifying Minerals
Color
Cleavage/Fracture
Streak
Hardness
Luster
Density
Crystal Systems
Special Properties
Color
• 1. Color is an easily
observed physical
property. Not the
best property to use
to identify because
many minerals like
quartz can come in a
variety of colors.
Identifying
Minerals
Streak
• Streak is the color of the minerals powder
when it is rubbed against a Streak Plate
– This property does not vary like the color of
the mineral can.
Identifying
Minerals
Luster
• Luster is used to describe how a mineral
reflects light from its surface.
• Metallic luster- looks
like a metal.
• Non-Metallic Lusterdoes not look like a
metal, can be glassy,
dull, earthy, waxy
and pearly.
Identifying
Minerals
Crystal Structure
• Each mineral grows atom to atom to form that
mineral’s particular structure.
– Classified into six groups (crystal systems) based
on the number and angle of the crystal faces.
Identifying
Minerals
Crystal Structure
• Particles of a mineral line up in a repeating
pattern. Forms a solid called a crystal.
– Has flat sides called faces, that meet at sharp
edges and corners.
5. Cleavage
• Cleavage- is a
mineral that easily
splits along flat
surfaces.
Identifying
Minerals
6 Fracture
• Fracture- describes
how a mineral looks
when it breaks apart in
an irregular way.
Identifying
Minerals
Special Properties
• Fluorescence- glows under UV (ultraviolet
light)
• Magnetic- acts like a magnet
• Radioactive- give off radiation- Uraninite
• Reacts to Acid- reacts by fizzing.
• Electrical Properties- electric current can be
produced (Quartz)
– Used in watches
Identifying
Minerals
Hardness
• The resistance to being scratched. One of the best clues.
• Mohs hardness scale.
– A scale from 1 to 10.
Identifying
Minerals
Mohs Hardness Scale see p150 to label
s
boxes with minerals
1.
2.
Softest known mineral.
It flakes when scratched by a
fingernail.
4.
A steel nail can easily
scratch it.
7.
Can scratch steel and hard
glass easily.
3.
A fingernail can easily
scratch it.
5.
Other Hardness’s
A fingernail cannot scratch
it, but a copper penny can.
6.
A steel nail can scratch it.
8.
Cannot be scratched by a
steel nail, but it can scratch
window glass.
9.
Can scratch quartz.
10.
Can scratch topaz.
Hardest known mineral,
Diamond can scratch all
other surfaces.
Identifying
Minerals
Density
• It is the mass in a given
volume.
• It always remains the
same for any given
mineral.
Identifying
Minerals
Density
• A balance would be used
to measure the mass of a
sample.
• The sample can be placed
in a graduated cylinder to
determine the volume.
Identifying
Minerals
Density
• Water Displacement (how much water is
moved, is equal to the volume of the
sample) is used to determine the volume of
the sample
Identifying
Minerals