CMU
Bill Palmer
Lecture 4
Central Methodist
University
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Natural
Chemically Pure
Make up “rocks”
Solid
Inorganic
Often form crystals
Crystal structure is
organized
arrangement of
atoms
MINERALS ARE
CHEMICALLY
PURE
ROCKS ARE
COMPOSED OF
MINERALS
Big important hint: Learn the Minerals and
the Rocks will be easy to learn!!
Your Very Life Depends on Minerals
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Between 2 - 3,000 have been identified
A few are “native elements” -- made of only one
element, such as sulfur, gold. copper, and
graphite (carbon)
Most are compounds, especially the silicate
group (Si, O)
Other important groups are oxides, carbonates,
and sulfides
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Quartz
Feldspar (group)
Muscovite (white
mica)
Biotite (black
mica)
Calcite
Pyroxene
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Olivine
Amphibole
(group)
Magnetite,
limonite, and
other iron oxides
Pyrite
Galena
Barite
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Aluminum--packaging, transport, building
Beryllium--gemstones, fluorescent lights
Copper--electric cables, wires, switches
Feldspar--glass and ceramics
Iron--buildings, automobiles, magnets
Calcite--toothpaste, construction
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Hardness
Crystal shape
(form)
Luster
Color
Streak
Learn how to test minerals
for these characteristics
instead of trying to memorize
each mineral!!
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Cleavage/fracture
Density (specific
gravity)
Special properties
--reaction to acid
--fluorescence
--salty taste
--magnetism
With 3,000 different minerals it
would be next to impossible to learn
all the names!!
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Ability to scratch
another mineral
Mohs scale from 1
(talc) to 10
(diamond)
Quartz (most
common mineral
and most dust
particles) is 7
HARDNESS OF SOME
COMMON ITEMS:
MOH’S SCALE
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2.5 Fingernail
2.5–3 Gold, Silver
3 Copper Penny
4-4.5 Platinum
4-5 Iron
5.5 Knife Blade
6-7 Glass
6.5 Iron Pyrite
7+ Hardened Steel File
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1 Talc Talcum powder.
2 Gypsum Plaster of Paris. Gypsum is
formed when seawater evaporates from
the Earth’s surface.
3 Calcite Limestone and most shells
contain calcite.
4 Fluorite Fluorine in fluorite prevents
tooth decay.
5 Apatite When you are hungry you
have a big "appetite".
6 Orthoclase Feldspar In German,
"feld" means "field".
7 Quartz Found everywhere.
8 Topaz The November birthstone.
Emerald and aquamarine are varieties of
beryl with a hardness of 8.
9 Corundum Sapphire and ruby are
varieties of corundum. Twice as hard as
topaz.
10 Diamond Used in jewelry and cutting
tools. Four times as hard as corundum.
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External structure
due to internal
arrangement of the
atoms
Six basic groups of
shapes, with about
three dozen
variations
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Describes how
light reflects off the
surface
Main categories are
“metallic” and
“non-metallic”
Non-metallic
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dull
glassy
waxy
pearly
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Results from ability
to absorb some
wavelengths and
reflect others
Some minerals have
characteristics
colors
Others vary due to
chemical differences
or impurities (atoms
mixed inside the
main elements)
COLOR is usually the worst
way to identify a mineral.
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Color of the powder
when rubbed on a
“streak plate”
(unglazed porcelain)
May be same as
hand-specimen or
different
Some paint is based
on powdered
minerals (streaks)
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Some minerals split along flat surfaces when
struck hard--this is called mineral cleavage
Other minerals break unevenly along rough or
curved surfaces--this is called fracture
A few minerals have both cleavage and
fracture
Due to how the atoms are arranged
Be sure you understand the difference between
CLEAVAGE and FRACTURE.
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All minerals have density
(mass / volume), but some
are very dense
Examples include galena,
magnetite, and gold
Specific Gravity is the
density of the mineral
compared with density of
water
Remember our Lab?
Some minerals just feel
“heavy”
Carbonates react
with dilute HCl and
other acids by
fizzing or bubbling
(releasing CO2
gas)
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Some minerals will
glow when placed
under short-wave
or long-wave
ultraviolet rays
Franklin and
Ogdensburg NJ
are famous for
their fluorescent
minerals
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DO NOT TASTE
MOST MINERALS!
Halite is the
exception--it will
taste salty
Kaolinite (clay) will
stick to your
tongue
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Magnetite
Many iron minerals
will produce an
invisible magnetic
force field
“Lodestone” was
used by Vikings
more than 1,000
years ago as
compasses
Or
Some common minerals that make-up most
rocks and some minerals your kids may ask you
what they are and you will want to know so you
can impress them.
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Very hard 7.0
Many, Many forms
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Clear
Rosy=pink
Milky=white
Smoky=black
Chalcedony=multicolor
Agate=color rings
Chert=white, brown, tan (very common)
Mozarkite=pink/purple bands (MO State Rock)
Amethyst=purple
Jasper=dark blood red
Jasper
Amethyst
Milky
Mozarkite
Chalcedony
Smoky
Agate
Rosy Quartz
Chert
Clear
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Hard 6.0
Vitreous, pearly
Good Cleavage,
breaks at 900
Plagioclase
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Sodium Calcium Aluminum
silicate
White, Yellow, Pink
Striations
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Orthoclase
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Potassium Aluminum Silicate
 White, yellow, pink
 NO Striations
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Check
the
Color
ORTHOCLASE pink
FELDSPAR
yes
light
Check for
Striations
dark PLAGIOCLASE
FELDSPAR
no
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Soft 2.5-3.0
“Saran Wrap”
Breaks in thin
layers
Biotite
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Dark
Muscovite
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Clear
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Soft 3.0
Excellent cleavage
in 3 directions
NOT 900
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Colorless
 White
 Yellowish
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Rhombohedrons
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Hard 5.5-6.0
“Augite”
Dark Green to
Gray
Eight-sided prisms
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Hard 7.0
White Streak
Pale to dark olive
Green
Peridot is the
Gemstone
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Hard 5.5
White to gray
Streak
Dark gray to black
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Iron Oxides
Iron Ores
Color Varies with
amount of Iron
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Limonite = yellow
Hematite = reddish
Magnetite = black
Tell apart by streak
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Hard 6.0-6.5
Dark gray Streak
Brassy yellow
“Fool’s Gold”
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Soft 2.5
Silver Gray
Metallic
Perfect Cubes
MO State Mineral
Source of Lead
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Soft 3.0-3.5
White, but can be
stained reddish
with iron
Heavy
“Tiff” of S MO
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1. Research the common uses for the 12
common minerals in the lecture.
2. List the diagnostic characteristics of minerals
and include some of the possible variations.
3. What is the difference between a rock and a
mineral?
4. Define a mineral.
5. What Moh’s Scale and what are some
hardness of some common objects.
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6. What is a crystal? Do all minerals form
crystals? What causes a crystal?
7. What is luster? What are the main types?
8. Distinguish between cleavage and fracture.
9. Why is color a poor distinguishing
characteristic when identifying minerals?
10. What is the Missouri State Mineral?
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www.mii.org
www.mineral.galleries.com/mineral
s
www.mineral.net
www.usgs.gov