Minerals
• Minerals are defined as (1) naturally
occurring, (2) inorganic substances
with a narrow range of (3) chemical
composition and (4) characteristic
physical properties.
• An example: The naturally occurring
form of the compound sodium
chloride is the mineral halite.
Minerals
• Minerals may be subdivided into two
majors groups:
– SILICATES
– NON-SILICATES
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
• The basic building
block of the silicates
is the silica
tetrahedron. Each
silicon atom is
attached to four
oxygen atoms by
tetahedral bonds. This
results in a 4- charge
on the Si04 group.
Minerals
There are many ways in which
the SiO4 tetrahedra can
be assembled to build
neutral silicate mineral
structures. These
structures are the major
rock-forming minerals.
•
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
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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,
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Fe+2)4 (Al, Fe+3)Si7AlO22(OH)2
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Double chains of
tetrahedra balanced by
similar cations.
Minerals
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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
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Feldspars
A second group of
alumino-silicates,
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 the
plagioclase feldspars.
Minerals
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Feldspars
A second group of
alumino-silicates,
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 the
plagioclase feldspars.
The K-feldspars or alkali
felspars:
•Microcline, (Potassium aluminum
silicate)
•Sanidine, (Potassium sodium
aluminum silicate)
•Orthoclase, (Potassium aluminum
silicate)
Minerals
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Feldspars
A second group of
alumino-silicates,
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 the
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
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Quartz
Silica tetrahedra alone
can form a neutral
three-dimensional
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
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Quartz SiO4
Silica tetrahedra alone
can form a neutral
three-dimensional
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
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Quartz
Silica tetrahedra alone
can form a neutral
three-dimensional
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
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Quartz
Silica tetrahedra alone
can form a neutral
three-dimensional
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
There are a few important groups of non-silicate minerals.
Only the carbonates are significant as rock-forming
minerals. The remaining mineral groups are often ore
minerals and provide economic sources for various
elements.
The important non-silicate groups are:
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Carbonates
Evaporites
Oxides
Sulphides
Phosphates
Minerals
Non silicates:
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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.
The 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:
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Oxides
oxides (hematite and magnetite)
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:
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Oxides
oxides (hematite and magnetite)
Fe2O3, Iron Oxide
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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:
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Oxides
oxides (hematite and magnetite)
Fe3O4, Iron Oxide
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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:
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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:
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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:
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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:
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Phosphates are relatively rare. The only important phosphate mineral is
apatite.
Ca2Fe(PO4)2 - 4H2O, Hydrated Calcium Iron Phosphate
Mineral properties
• Minerals are distinguished by their physical and
chemical properties.
• The same properties are responsible for the
many of the mechanical characteristics of rocks.
• Most common minerals can be recognized from
one or two characteristics.
Mineral properties
• PHYSICAL CHARACTERISTICS:
1. Colour The colour of minerals is rarely diagnostic when used alone
but some minerals (native sulphur - YELLOW, amethyst quartz PURPLE, hematite - RED, azurite - BLUE GREEN) are very
distinctively coloured.
Mineral properties
• PHYSICAL CHARACTERISTICS:
2. Lustre Lustre is the way in which light is reflected from
mineral surfaces and is more frequently diagnostic than
colour. Metallic lustre is often found in sulphide minerals,
non-metallic lustres include glassy, dull and earthy.
Mineral properties
• PHYSICAL CHARACTERISTICS:
3. Transparency The ability to see through a mineral is a
measure of transparency. Reflecting surfaces are called
translucent.
Mineral properties
• PHYSICAL CHARACTERISTICS:
4. Crystal System Crystal symmetry is a very important
diagnostic aid. Minerals fall into one of seven crystal
classes.
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.
Mineral properties
• PHYSICAL CHARACTERISTICS:
5. Crystal Habits This is the name given to the form or
shape of crystals. Cubic, dodecahdral, octahedral,
rhombohdral, prismatic, columnar, pinacoidal and
pyramidal are a few of the many forms that crystal can
display.
Mineral properties
• PHYSICAL CHARACTERISTICS:
6. Cleavage This refers to the characteristic manner in
which minerals split along planes determined by their
crystal structure. Mica has a perfect basal cleavage in
one direction and splits into thin sheets. Feldspars
commonly show two strong cleavages. Cubic minerals such
as halite often display three mutually orthogonal cleavage
directions.
Mineral properties
• PHYSICAL CHARACTERISTICS:
7. Fracture Fracture is mineral breakage which is
unrelated to crystal structure. Quartz has no cleavage
but can often show conchoidal fracture patterns.
Mineral properties
• PHYSICAL CHARACTERISTICS:
8. Hardness Mineral hardness is measured on a non-linear
relative scale called Mohs Scale of Hardness
Mineral properties
• PHYSICAL CHARACTERISTICS:
8. Hardness Mineral hardness is measured on a non-linear relative scale called
Mohs Scale of Hardness
HARDNESS
1
2
3
4
5
6
7
8
9
10
MINERAL
Talc
Gypsum
Calcite
Fluorite
Apatite
Orthoclase
Quartz
Topaz
Corundum
Diamond
COMMON EXAMPLE
Pencil lead 1.0-2.0
Fingernail 2.5
Copper penny 3.5, brass
Iron
Tooth enamel, knife blade, glass 5.5-6.0
Steel file 6.5
Scratches glass
-----Saphire, ruby
Synthetic diamond
Mineral properties
• PHYSICAL CHARACTERISTICS:
9. Specific Gravity S.G. is an easily measured physical
property that can be readily estimated. In general,
sulphides and oxides have much higher specific gravities
than silicates.
Mineral properties
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PHYSICAL CHARACTERISTICS:
9. Specific Gravity S.G. is an easily measured physical property that can be readily
estimated. In general, sulphides and oxides have much higher specific gravities than
silicates.
MINERAL GROUP
MINERAL
SPECIFIC GRAVITY
Framework Silicate
Quartz
2.6-2.7
Framework Silicate
Feldspar
2.6-2.7
Sheet Silicate
Mica
2.8-3.0
Chain Silicate
Amphibole
2.9-3.2
Chain Silicate
Pyroxene
3.2-3.6
Isolated Silicate
Olivine
3.3-4.4
Isolated Silicate
Garnet
3.5-4.4
Sulphide
Sphalerite
4.0
Sulphide
Chalcopyrite
4.2
Sulphide
Pyrite
5.0
Oxide
Magnetite
5.2
Oxide
Hematite
5.3
Sulphide
Galena
7.2
Oxide
Pitchblende
9.5
Element
Native Gold
12.4
Mineral properties
• PHYSICAL CHARACTERISTICS:
10. Streak Streak is the name given to the colour of a
mineral when powdered by abraision against a stronger
material (usually a ceramic or porcellain plate). Streak is
a much more useful diagnostic characteristic than colour.
Mineral properties
• PHYSICAL CHARACTERISTICS:
11. Other Characteristics: Some minerals have special
characteristics that are diagnostic for only a few
species. Refractive index (calcite), effervescence with
dilute acids (calcite), fluorescence (fluorite),
phosphorescence, piezoelectricity (quartz), resistivity
(halite), taste (halite) and magnetic properties
(magnetite) are all used to identify particular minerals.
Common minerals
• the most common minerals you'll find in rocks
”rock forming minerals”
• This pile contains plagioclase feldspar, potassium
feldspar, quartz, muscovite mica, biotite mica,
amphibole, olivine, and calcite.
Lab - common minerals
• You must print out the instructions from internet
http://www.lwr.kth.se/Grundutbildning/1B1035/oevningar/Mineralidentifikation.pdf
• Your are to work in groups
• First read the entire mineral lab instructions
• Your are to try to identify the minerals by determining their physical
properties (check in the course text book chapter 2)
• When you think you have identified them correctly – ASK an
assistent to check them
• Learn to recognize them
• Change boxes with another group and test if you can identify them
when they look a bit differently
• Check the minerals that are in the large demonstration boxes at the
front of the class to see how differently they look
Minerals – what you need to know!
• Oral test
– Name of the mineral and
– Mineral group
– Limited time, 5 min
• Written test
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Definition of a mineral
Physical properties of minerals
Hardness scale
Mineral groups
Recognize the mineral names we learn in the lab as a mineral