All Minerals
1.
2.
3.
4.
Are formed by naturallly
Are NOT alive (inorganic)
Are solid
Are elements or compounds with a unique
chemical makeup
5. Are made up of particles that are arranged
in a pattern that is repeated over and over
(called a CRYSTAL)
Rock Forming Minerals
Common minerals that make up the Earth’s
crust
Groups of Minerals
• Minerals are grouped by the elements
they are made of.
Beryl (Emerald)
Calcite
Amethyst
Mineral Group
Silicates
Characteristics
Examples
•Contain oxygen Quartz, mica
& silica
•The most
abundant group
of minerals
MICA
Quartz
Mineral Group
Non-Silicates
Silver
Characteristics
•Make up only
5% of the
Earth’s crust
•Include some
of the most
important
minerals
Examples
iron, copper,
gold, silver,
diamonds,
rubies
Copper
Diamond
Gold
Ruby
Iron
Mineral Group
Carbonates
Characteristics
Examples
•Carbon &
Calcite (CaCO3)
oxygen and a
positive ion,
such as calcium
Calcite with Duftite inclusions
Mineral Group
Oxides
Characteristics
Metallic ion
and oxygen
Examples
Hematite
(Fe2)O3
Mineral Group
Sulfides
Characteristics
Sulfur and a
metallic ion
Examples
Galena (PbS)
Mineral Group
Sulfates
Barite on Calcite
BaSo4 / CaCO3
Characteristics
Metallic ion,
Sulfur &
oxygen
Barite
BaSo4
Examples
Barite (BaSO4)
Mineral Group
Native
Elements
Characteristics
Single
elements
Examples
Gold (Au),
Diamond (C),
Silver (Ag)
How do minerals form?
• 1) Cooling of magma (hot, liquid rock
and minerals inside the earth (from
the mantle))
– Fast Cooling = No Crystals (mineraloids)
– Medium Cooling = small crystals
– Slow Cooling = large crystals
How do minerals form?
• 2) Elements dissolved in liquids
(water)
Physical Properties of Minerals
(can be used to identify the mineral)
Color
• Can be misleading
• Can vary with the type of impurities
Physical Properties of Minerals
(can be used to identify the mineral)
Luster
• Surface reflection
• metallic = shiny
like metal
• non-metallic = dull,
non-shiny surface
Pyrite has a metallic luster
Calcite has a non-metallic luster
Physical Properties of Minerals
(can be used to identify the mineral)
Streak
• The color of the powdered
form of the mineral
• The color of the streak
can be different than the
mineral
• Minerals must be softer
than the streak plate
Physical Properties of Minerals
(can be used to identify the mineral)
Hardness
• How easily a mineral scratches
materials
• Mohs Hardness Scale
• Scale from 1 (softest) to 10 (hardest)
• Test by seeing if the mineral can scratch
different objects (like human fingernail,
copper, penny, glass, steel file)
Physical Properties of Minerals
(can be used to identify the mineral)
Cleavage & Fracture
– The way the mineral breaks
– Cleavage—minerals break
along smooth, flat surfaces
and every fragment has the
same general shape
– Fracture—minerals that break
at random with rough or
jagged edges
Cleavage or Fracture?
1.
4.
2.
3.
Physical Properties of Minerals
(can be used to identify the mineral)
Other Properties
– Specific gravity =
dry mass
mass lost in water
– Attraction to magnets
– Reaction with hydrochloric acid
– Smell & taste
Definition of a Mineral
“A naturally occurring, inorganic, solid
element or compound with a definite
chemical composition and a regular
internal crystal structure.”
Mineral Characteristics
• Chemical composition
– Diamond = graphite (both are pure carbon)
• Crystal structure
– Diamond ≠ graphite
Halite Crystal
Source: Photograph © The McGraw-Hill Companies, Inc./Bob Coyle, photographer.
Galena
Source: Photograph © The McGraw-Hill Companies, Inc./Doug Sherman, photographer.
Fluorite
Source: Photograph © The McGraw-Hill Companies, Inc./Doug Sherman, photographer.
Halite
Source: Photograph © The McGraw-Hill Companies, Inc./Doug Sherman, photographer.
Cubic Structure of Halite
Source: Photograph © The McGraw-Hill Companies, Inc./Bob Coyle, photographer.
Mineral Properties
• Hardness (Mohs hardness scale)
– See appendix C
• Cleavage (how it breaks- atomic scale)
• Luster- the surface ‘sheen’
• Color is not a good property for i.d.
– Corundum (Al2O3)
Minerals: two groups
• Silicates (Si + O ± other elements)
–
–
–
–
–
–
–
All built with ‘silicon tetrahedra’
4 O atoms, 1 Si atom, 4- charge
Quartz, feldspars
Olivine (peridot) ferromagnesian (Fe, Mg)
Asbestos
Micas
Clays (tropical weathering)
Minerals: non-silicates
• Nonsilicates
–
–
–
–
–
–
–
Example
Carbonates (CO3):
calcite
Sulfates (SO4):
gypsum
Sulfides (metal + S):
pyrite
Oxides (metal + O):
hematite
Hydroxides (metal + OH):
gibbsite
Halides (metal + halide):
salt (halite)
Native elements
Au, Ag, Pt, Cu, C
Labradorite has labradorescence or chatoyance.
LABRADORITE
A. FELDSPARS (two varieties to identify)
All have two directions of cleavage.
2. ORTHOCLASE (pink, tan or white) KAlSi308
Has stringers that go through the mineral
- looks superficially like striations.
Look at display so that you know what striations are.
ORTHOCLASE
B. FERROMAGNESIANS (iron and magnesium silicates)
All have two directions of cleavage.
1. AMPHIBOLES (2 types to identify)
Cleavage planes intersect forming 124o and 56o
cleavage angles.
Crystals usually long and thin.
a. HORNBLENDE (black)
Cleavage Angles
A. FELDSPARS (two varieties to identify)
All have two directions of cleavage.
1. PLAGIOCLASE (2 types to identify) (Ca,Na)(Si,Al)4O8
Have striations on cleavage planes
(end at edge of cleavage plane).
a. OLIGOCLASE (white) Na-rich feldspar
b. LABRADORITE (gray to black) Ca-rich feldspar
STRIATIONS
OLIGOCLASE
LABRADORITE
b. ACTINOLITE (greenish gray or grayish green)
Crystals usually in radiating masses
(check with me if not visible!)
ACTINOLITE
2. PYROXENES (1 to identify)
Cleavage planes intersect forming
88o and 92o cleavage angles.
Crystals usually short and stubby.
a. AUGITE (greenish black)
AUGITE
C. MICAS (3 to identify)
All have one direction of cleavage, producing
platy appearance.
1. MUSCOVITE (white-silver)
2. BIOTITE (brown)
3. CHLORITE (green) - may not look like the
other micas in terms of plateyness.
Chlorite
D. QUARTZ (SiO2)
Hardness is 7.
Can be many colors due to impurities.
Displays conchoidal fracture.
ROSE QUARTZ
AMETHYST
CONCHOIDAL FRACTURE
E. OLIVINE
Olivine is olive green.
Granular appearance.
May be able to see conchoidal fracture of grains
with hand lens.
F. CALCITE (CaCO3)
Fizzes or effervesces in HCl.
Three directions of cleavage not at right angles
(rhombohedral cleavage).
Clear pieces may exhibit double refraction.
RHOMBOHEDRAL
CLEAVAGE
HCl ACID REACTION
DOUBLE REFRACTION
G. GARNET
Reddish-brown color (but can be others).
Has hackly fracture, no cleavage.
Roundish crystals with 12-24 flat faces
readily visible in most cases.
H. STAUROLITE
Crystals usually twinned ("fairy crosses").
Mineral appearance
• color (not very useful)
Pyrite
Gold
Hardness
Mohs Hardness Scale
Mineral
Rating
Testing Method
Talc
1
Softest known mineral. It flakes easily when
scratched by a fingernail.
Gypsum
Calcite
2
A fingernail can easily scratch it.
3
A fingernail cannot scratch it, but a copper
penny can.
Fluorite
Apatite
Feldspar
4
A steel knife can easily scratch it.
5
A steel knife can scratch it.
6
Cannot be scratched by a steel knife, but it
can scratch window glass.
Quartz
Topaz
Corundum
Diamond
7
Can scratch steel and hard glass easily.
8
Can scratch quartz.
9
Can scratch topaz.
10
Hardest known mineral. Diamond can
scratch all other substances.
Luster
• The way a mineral reflects a light luster.
• Either metallic or nonmetallic
Specific Gravity
• The specific gravity of a mineral is the
ration of its weight compared with the
weight of an equal volume of water.
• Gold has specific gravity of 19
• It means gold is 19 times heavier than
water.
19 times heavier
Specific Gravity
Streak
• When a mineral is rubbed across a piece of
porcelain tile a streak of powdered mineral
is left behind.
Cleavage
• Cleavage is the way that mineral breaks.
• Minerals that break along smooth, flat
surfaces have cleavage.
• Mica has cleavage
Fracture
• Mineral that breaks uneven, rough, or
jagged surfaces have fracture.
• Quartz has fracture
quartz
Identify the minerals below for
cleavage and fracture
CLEAVAGE
FRACTURE
Uncut and cut Diamonds (C)
Some examples of minerals…
This is pyrite (FeS2),
also known as “Fool’s Gold.”
Common Mineral...
Crystal Quartz
Milky Quartz
(SiO2)
Rare Mineral...
This is also a variety of quartz (a rarer gem variety).
SiO2, + Fe and Mn (that reflects purple light)
Another Rare Mineral
Mica (lepidolite) that has a purplish appearance.
emerald
Gemstones:
sapphire
ruby
tourmaline
sapphire
Chemical Composition
Each mineral has a unique chemical composition which
makes it different from all other minerals.
Examples:
Copper
Gold
Halite
Quartz
Calcite
Corundum
Beryl
Ruby
Diamond
Cu
Au
NaCl
SiO2
CaCO3
Al2O3
Be3Al2Si6O18
Al2O3
C
Minerals Have a Crystal Structure
In addition to a unique
chemical composition,
each mineral has a
definite structure.
Crystal structure: the
repeating pattern of
how the atoms in the
mineral are bonded
together.
When a mineral forms,
it can show this
overall crystal
structure.
Crystal Forms of Carbon
These are eight different crystal forms of carbon: diamond, graphite,
lonsdaleite, C60, C540, C70, amorphous carbon and a carbon nanotube
Minerals
• Silicates are by far the
most abundant mineral
group accounting for more
than 90% of the Earth's
crust. Silicates are the
major rock-forming
minerals. It follows that
oxygen and silicon are the
most abundant elements in
the crust.
Minerals
There are many ways in which
the SiO4 tetrahedra can be
assembled to build neutral
silicate mineral structures.
Isolated tetrahedra balanced
by the cations magnesium
(Mg), iron (Fe),calcium (Ca)
–
–
Olivines (Mg, Fe)2SiO4,
Magnesium Iron
Silicate
and Garnets
Minerals
The typical pyroxene
structure contains chains
of SiO3 tetrahedrons
•
The slope of the
tetrahedral pyramids
helps to determine the
cleavage angle of the
pyroxenes at nearly 90o
degrees (actually 93o
and 87o).
Minerals
•
•
•
•
•
•
•
•
•
•
common amphiboles:
Actinolite Ca2(Mg, Fe+2)5 Si8O22(OH)2
Anthophyllite (Mg, Fe)7 Si8O22(OH)2
Arfvedsonite Na3(Fe+2)4Fe+3
Si8O22(OH)2
Cummingtonite Mg7 Si8O22(OH)2
Edenite NaCa2Mg5 Si8O22(OH)2
Fluorrichterite Na(CaNa)Mg5 Si8O22F2
Glaucophane Na2(Mg3Al2) Si8O22(OH)2
The Hornblende Series Ca2(Mg, Fe+2)4
(Al, Fe+3)Si7AlO22(OH)2
Double chains of tetrahedra balanced by
similar cations.
Minerals
•
•
•
Micas and Clay Minerals
Sheets of tetrahedra are the
building blocks.
Aluminum is also involved
in these sheet structures
which are charge-balanced
by the cations Mg, Na and
K.
most common mica
minerals: muscovite,
biotite
Minerals
•
•
•
•
•
Feldspars
A second group of aluminosilicates,
tetrahedra form threedimensional frameworks
with Ca, Na and K as the
The K-feldspars or alkali
balancing cations.
felspars:
The very abundant
•Microcline, (Potassium aluminum
feldspar are subdivided in
silicate)
K-Na bearing alkali
•Sanidine, (Potassium sodium
aluminum silicate)
feldspars and the
Ca-Na solid-solution series •Orthoclase, (Potassium aluminum
silicate)
called plagioclase feldspars.
Minerals
•
•
•
•
•
Feldspars
A second group of aluminosilicates,
tetrahedra form threedimensional frameworks with
Ca, Na and K as the balancing
cations.
The very abundant
feldspar are subdivided in
K-Na bearing alkali
feldspars and the
Ca-Na solid-solution series
called plagioclase feldspars.
The plagioclase feldspars:
•Albite, (Sodium aluminum silicate)
•Oligoclase, (Sodium calcium
aluminum silicate)
•Andesine, (Sodium calcium
aluminum silicate)
•Labradorite, (Calcium sodium
aluminum silicate)
•Bytownite, (Calcium sodium
aluminum silicate)
•Anorthite, (Calcium aluminum
silicate)
Minerals
•
•
Quartz
Silica tetrahedra alone can
form a neutral threedimensional framework
structure with no need for
other cations.
This arrangement forms a very
stable structure
popular as ornamental stone and as gemstones
•Amethyst is the purple gemstone variety.
•Citrine is a yellow to orange gemstone variety that is rare in nature but is often
created by heating Amethyst.
•Milky Quartz is the cloudy white variety.
•Rock crystal is the clear variety that is also used as a gemstone.
•Rose quartz is a pink to reddish pink variety.
•Smoky quartz is the brown to gray variety.
Minerals
•
•
Quartz SiO4
Silica tetrahedra alone
can form a neutral threedimensional framework
structure with no need
for other cations.
This arrangement forms a
very stable structure
popular as ornamental stone and as gemstones
•Amethyst is the purple gemstone variety.
•Citrine is a yellow to orange gemstone variety that is rare in nature but is often
created by heating Amethyst.
•Milky Quartz is the cloudy white variety.
•Rock crystal is the clear variety that is also used as a gemstone.
•Rose quartz is a pink to reddish pink variety.
•Smoky quartz is the brown to gray variety.
Minerals
•
•
Quartz
Silica tetrahedra alone
can form a neutral threedimensional framework
structure with no need
for other cations.
This arrangement forms a
very stable structure
popular as ornamental stone and as gemstones
•Amethyst is the purple gemstone variety.
•Citrine is a yellow to orange gemstone variety that is rare in nature but is
often created by heating Amethyst.
•Milky Quartz is the cloudy white variety.
•Rock crystal is the clear variety that is also used as a gemstone.
•Rose quartz is a pink to reddish pink variety.
•Smoky quartz is the brown to gray variety.
Minerals
•
•
Quartz
Silica tetrahedra alone
can form a neutral threedimensional framework
structure with no need for
other cations.
This arrangement forms a
very stable structure
popular as ornamental stone and as gemstones
•Amethyst is the purple gemstone variety.
•Citrine is a yellow to orange gemstone variety that is rare in nature but is often
created by heating Amethyst.
•Milky Quartz is the cloudy white variety.
•Rock crystal is the clear variety that is also used as a gemstone.
•Rose quartz is a pink to reddish pink variety.
•Smoky quartz is the brown to gray variety.
Minerals
Non-silicates:
• Carbonates: CO3
• The important carbonates are the minerals calcite and dolomite. Both are
significant rock-forming minerals.
• The Calcite Group:
• Calcite (Calcium Carbonate)
• Gaspeite (Nickel Magnesium Iron Carbonate)
• Magnesite (Magnesium Carbonate)
• Otavite (Cadmium Carbonate)
• Rhodochrosite (Manganese Carbonate)
• Siderite (Iron Carbonate)
• Smithsonite (Zinc Carbonate)
• Sphaerocobaltite (Cobalt Carbonate)
Minerals
Non-silicates:
• Evaporites:
halides including the minerals halite, sylvite and fluorite;
sulphates including the minerals gypsum and anhydrite.
Most famous halide mineral, halite (NaCl) or rock salt
Minerals
Non-silicates:
• Evaporites:
halides including the minerals halite, sylvite and fluorite;
sulphates including the minerals gypsum and anhydrite.
•Fluorite: CaF2, Calcium Fluoride
Minerals
Non-silicates:
• Evaporites:
halides including the minerals halite, sylvite and fluorite;
sulphates including the minerals gypsum and anhydrite.
•Gypsum:CaSO4-2(H2O), Hydrated Calcium Sulfate
Minerals
Non-silicates:
• Oxides
• oxides (hematite and magnetite)
Fe2O3, Iron Oxide
•
•
•
•
hydroxides (limonite and goerthite)
important minor consituents in rocks.
aluminum oxide bauxite can also occur as a rock-forming mineral.
oxide minerals are exploited as economic sources of many elements including
aluminum, antimony, iron, manganese, tin, and uranium.
Minerals
Non-silicates:
• Oxides
• oxides (hematite and magnetite)
Fe3O4, Iron Oxide
•
•
•
•
hydroxides (limonite and goerthite)
important minor consituents in rocks.
aluminum oxide bauxite can also occur as a rock-forming mineral.
oxide minerals are exploited as economic sources of many elements including
aluminum, antimony, iron, manganese, tin, and uranium.
Minerals
Non-silicates:
• Sulphides
• The mineral pyrite is the only sulphide that occurs commonly in rocks.
• Sulphides are most important as economic minerals providing the main sources
of elements such as arsenic, copper, lead, nickel, mercury, molybdenum and
zinc.
• FeS2, Iron Sulfide
Minerals
Non-silicates:
• Sulphides
• The mineral pyrite is the only sulphide that occurs commonly in rocks.
• Sulphides are most important as economic minerals providing the main sources
of elements such as arsenic, copper, lead, nickel, mercury, molybdenum and
zinc.
• PbS, Lead Sulfide, Galena
Minerals
Non-silicates:
• Sulphides
• The mineral pyrite is the only
sulphide that occurs commonly
in rocks.
• Sulphides are most important as
economic minerals providing
the main sources of elements
such as arsenic, copper, lead,
nickel, mercury, molybdenum
and zinc.
• CuFeS2, Copper Iron Sulfide,
Chalcopyrite
Minerals
Non-silicates:
• Phosphates are relatively rare. The only important phosphate mineral is apatite.
• Ca2Fe(PO4)2 - 4H2O, Hydrated Calcium Iron Phosphate
Crystal System
ISOMETRIC
TETRAGONAL
ORTHORHOMBIC
MONOCLINIC
DIAMOND
TANZANITE
WULFENITE
GYPSUM
HEXAGONAL
TRIGONAL
BERYL
QUARTZ
variety - AMETHYST
TRICLINIC
AMORPHOUS
MONTEBRASITE
AMBER
Crystal System
SEVEN CRYSTALLOGRAPHIC SYSTEMS:
1. ISOMETRIC,
2.
3.
4.
5.
requires 4 three fold axis of rotation.
TETRAGONAL, requires 1 four fold axis of rotation.
HEXAGONAL, requires 1 six fold axis of rotation.
TRIGONAL, requires 1 three fold axis of rotation.
ORTHORHOMBIC, requires either 3 two fold axis of rotation or 1
two fold axis of rotation and two mirror planes.
6. MONOCLINIC, requires either 1 two fold axis of rotation or 1
mirror plane.
7. TRICLINIC, requires either a center or only translational
symmetry.
AMORPHOUS; no symmetry is present and it is therefore not a
crystallographic system.
Common Minerals
• the most common minerals you'll find in rocks ”rock
forming minerals”
• These contain plagioclase feldspar, potassium feldspar, quartz,
muscovite mica, biotite mica, amphibole, olivine, and calcite.
Minerals
Dr. R. B. Schultz
The earth is made of rocks…
and rock are made of minerals.
Minerals are:
·
1. Naturally occurring,
·
2. Inorganic,
·
3. Have known chemical compositions
·
4. Have definite physical properties.
5. Are solid
·
They are usually crystalline.
Mineral Classification
Minerals are classified based on chemical
composition and crystal structure.
Minerals are made of different ions bonded
together.
Ions are charged atoms

Cations are + charged

Anions are - charged
Common ions in earth's crust:
O - most common ion (anion)
Si, Al, Fe, Ca, Na, K, Mg, (Cations)
Crystal structure depends on sizes of and
charges on ions
Most common mineral group is the silicates
All silicate minerals contain silicon and oxygen
1. Mafic silicate minerals contain iron or
magnesium and are dark in color.
Examples: olivine, pyroxene, amphibole, and
biotite mica
2. Felsic silicates don't contain magnesium or
iron, and are light in color.
Examples: feldspar, quartz, clay minerals,
muscovite mica
Mafic silicate
Felsic silicate
Silica
Tetrahedron
Oxygens
Silicon
Common non-silicate minerals
Fluorite – used as a toothpaste additive
Calcite -- calcium carbonate -- Limestone is made of
calcite.
Dolomite -- calcium magnesium carbonate
Gypsum -- calcium sulfate
Galena -- lead sulfide
Pyrite -- iron sulfide
Halite -- sodium chloride (table salt)
Non-Metallic
Mineral
Luster
the way a
mineral
reflects
Metallic
Mineral
Cleavage
Refers to very smooth, flat, shiny breakage
surfaces
These special breakage surfaces correspond to
zones of weak bonding in the crystal structure.
To describe cleavage, one must determine the
number of unique cleavage planes (directions)
NO
Cleavage
Hardness
Refers to "scratchability" or resistance to being
scratched. Harder minerals will scratch softer minerals.
Geologists rank minerals according to hardness using the
Moh's scale
1.0
2.0
2.5
3.0
3.5
4.0
5.0
5.5
6.0
7.0
8.0
9.0
10.0
TALC
GYPSUM
FINGERNAIL
CALCITE
COPPER PENNY
FLUORITE (Note the spelling!)
APATITE
STEEL KNIFE BLADE/GLASS PLATE
ORTHOCLASE FELDSPAR
QUARTZ
TOPAZ
CORUNDUM (RUBY)
DIAMOND
Color
Varies in many minerals, e.g. quartz
VERY unreliable.
Some minerals come in just one color;
other are many colors/many varieties.
Streak
Refers to color of mark left by rubbing mineral against a
streak plate (unglazed porcelain). Streak does not vary
even if color does.
Other Properties
Some minerals are magnetic (i.e., magnetite)
Some minerals effervesce ("fizz") in dilute acid (calcite)
Specific gravity (like density) galena-high specific gravity.