Transcript Document

Elements and Compounds in their
solid form make up…
What is a Mineral?
A Mineral is a naturally
occurring Inorganic Solid with a
definite chemical composition and
a crystalline structure.
That means that…
•It can’t be organic in
origin
•It can’t be a liquid
and..
•It has to have a crystal
structure
5 Requirements
1. Mineral are naturally occurring
substances.
2. Minerals are solids.
3. Minerals have a definite
chemical composition (i.e. they
are elements or compounds, NOT
mixtures).
4. The atoms that make up minerals
are arranged in an orderly pattern
(They form crystals).
5. Minerals are inorganic. (They
were never alive.) (Some scientists do classify a
few substances as organic minerals, but that is going outside
the accepted definition.)
How many different minerals are
there on Earth???
Answer:About 4,000
Silicon and Oxygen are the two
most abundant elements in
Earth’s crust.
Oxygen makes up about 47% by
mass of the Earth’s crust and
Silicon is about 28%.
Composition of the Earth’s Crust
 Eight Elements that make up over 98% of
Earth’s Crust
-Oxygen (O)
-Silicon (Si)
-Aluminum (Al)
-Iron (Fe)
-Calcium (Ca)
-Sodium (Na)
-Potassium (K)
-Magnesium (Mg)
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 SiO4-4 group.
And…..
The percent composition of Silicate
Minerals in an igneous rock determine a
lot of the characteristics of that rock and
the magma that formed it.
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)
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Olivine (Mg, Fe)2SiO4,
Magnesium Iron Silicate
and Garnet
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 include:
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Actinolite Ca2(Mg, Fe+2)5
Si8O22(OH)2
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Anthophyllite (Mg, Fe)7 Si8O22(OH)2
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Arfvedsonite Na3(Fe+2)4Fe+3
Si8O22(OH)2
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Cummingtonite Mg7 Si8O22(OH)2
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Edenite NaCa2Mg5 Si8O22(OH)2
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Fluorrichterite Na(CaNa)Mg5
Si8O22F2
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Glaucophane Na2(Mg3Al2)
Si8O22(OH)2
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The Hornblende Series Ca2(Mg,
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 aluminosilicates.
Tetrahedra form threedimensional frameworks
with Ca, Na and K as the
balancing cations.
They are very abundant.
Feldspars are subdivided into
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 aluminosilicates.
Tetrahedra form threedimensional frameworks
with Ca, Na and K as the
balancing cations.
They are very abundant.
Feldspars are subdivided into
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 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
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Quartz SiO2
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
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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
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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
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
Halides
Oxides and Hydroxides
Sulfides (and Sulfates)
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:
• Evaporite: A mineral or substance that forms as a precipitate (solid) as water it was
dissolved in evaporates.
Halides including the minerals halite, sylvite and fluorite;
Sulfates including the minerals gypsum and anhydrite.
The most famous halide mineral, halite (NaCl) or rock salt
Minerals
Non-silicates:
• Evaporite: A mineral or substance that forms as a precipitate (solid) as water it was
dissolved in evaporates.
Halides including the minerals halite, sylvite and fluorite;
Sulfates including the minerals gypsum and anhydrite.
•Fluorite: CaF2, Calcium Fluoride
Minerals
Non-silicates:
• Evaporite: A mineral or substance that forms as a precipitate (solid) as water it was
dissolved in evaporates.
Halides including the minerals halite, sylvite and fluorite;
Sulfates including the minerals gypsum and anhydrite.
•Gypsum:CaSO4-2(H2O), Hydrated Calcium Sulfate
Minerals
Non-silicates:
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Oxides and Hydroxides
Oxides include minerals like hematite (Fe2O3) and magnetite (Fe3O4)
Hydroxides include minerals like limonite (actually a mixture of iron (III) oxides and
hydroxides) and goethite (FeO(OH)).
Important minor constituents 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 goethite)
Important minor constituents 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 goethite)
Important minor constituents 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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Sulfides
The mineral pyrite is the only sulfide that occurs commonly in rocks.
Sulfides 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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Sulfides
The mineral pyrite is the only sulfide that occurs commonly in rocks.
Sulfides 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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Sulfides
The mineral pyrite is the only
sulfide that occurs commonly in
rocks.
Sulfides 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
A Bit More on Silicates
High Silica content forms lightcolored rocks.
While lower (but only by about
25%) Silica content forms
darker-colored rocks.
How do Minerals Form???
1. Minerals form in cooling magma chambers
- usually combining into igneous rocks like
granite.
Different types of minerals
crystallize at different temperatures
Decreasing temperature
Bowen’s Reaction Series
Mineral formation in a Magma Chamber
Some Common Minerals and
Rocks that Form from Cooling
and Crystallizing Magma
Olivine
Pyroxene
Peridotite - Mostly Olivine
Gabbro- Pyroxene and Olivine
Andesite- Hornblend and Biotite and
Plagioclase Feldspar
Potassium Feldspar
Pink Granite
Mineral Fractionalization in a Magma Chamber
2. Metamorphic Minerals:
Some minerals occur as the
result of Recrystallization and
Reaction within existing rocks
which produces new minerals
in response to changes in
and
3. Some types of minerals form
as water containing dissolved
ions slowly evaporates (i.e.
evaporites that precipitate out).
Salt deposits
4. Hydrothermal Solutions
• The last way that minerals can form is when hot
water solutions containing dissolved substances
(i.e. hydrothermal solutions) come into contact
with existing minerals.
• This contact can lead to chemical reactions that
form new minerals.
• Also, when these solutions cool some of the
elements in them combine to form minerals like
quartz and pyrite.
Quartz
How long does it take for
minerals to form?
• Minerals in solution in water can form
relatively quickly when the water
evaporates.
• Minerals in magma can form as quickly as
the magma/lava can crystallize (lava can
cool in minutes, while magma can take
thousands of years).
A Crystal is….
A regular geometric solid with
smooth surfaces called….
The orderly arrangement of ions,
molecules, or atoms, in any
mineral determines the shape of
its crystals.
Although there are thousands of
different types of minerals, their
crystals come in six basic types
of shapes
CRYSTAL HABIT
• The crystal habit of a mineral describes its
visible external shape. It can apply to an
individual crystal or an assembly of crystals.
• Each crystal can be described by how well it is
formed, ranging from euhedral (perfect to
near-perfect), to subhedral (moderately
formed), and anhedral (poorly formed to no
discernable habit seen).
Habit
Image
Description
Common Example(s)
Acicular
Needle-like,
slender and/or
tapered
Natrolite, Rutile
Amygdaloidal
Almond-shaped
Heulandite,
subhedral Zircon
Bladed
Blade-like,
slender and
flattened
Actinolite, Kyanite
Botryoidal or
globular
Grape-like,
hemispherical
masses
Hematite, Pyrite,
Malachite, Smithsonite,
Hemimorphite,
Adamite, Variscite
Habit
Columnar
Coxcomb
Image
Description
Similar to fibrous:
Long, slender
prisms often with
parallel growth
Aggregated flaky
or tabular crystals
closely spaced.
Common
Example(s)
Calcite, Gypsum/
Selenite
Barite, Marcasite
Pyrite, Galena,
Halite
Cubic
Cube shape
Dendritic or
arborescent
Pyrolusite and
Tree-like,
other Mn-oxide
branching in one
minerals,
or more direction
Magnesite,
from central point.
native copper
Habit
Dodecahedral
Image
Description
Common Examples
Dodecahedron, 12-sided
Garnet
Drusy or
encrustation
Aggregate of minute
crystals coating a surface
or cavity
Uvarovite, Malachite, Azu
rite
Enantiomorphic
Mirror-image habit
(i.e. crystal twinning) and
optical characteristics;
right- and left-handed
crystals
Quartz, Plagioclase,
Staurolite
Equant, stout
Length, width, and
breadth roughly equal
Olivine, Garnet
Extremely slender prisms
Serpentine
group, Tremolite (i.e. Asb
estos)
Fibrous
Crystal Habit
• There are many more additional habits to
ones listed here.
• Also remember that these habits do not
always form well – in many cases they are
distorted and in some cases they are are
indistinguishable.
Only 30 of the 4,000 known
minerals are common.
These 30 minerals are known
as the rock-forming minerals
Most rock-forming minerals
are…
The percent composition
of Silicate minerals in a
rock determines the type
of rock it is.
Rocks are often made of several
different minerals.
Rocks that have a high percentage
of Silicates are light in color, and
are called Felsic rocks.
Rocks that have a low
percentage of Silicates are dark
in color, and are called
Mafic rocks.
Minerals are identified and classified by
visual inspection, and by performing
simple tests to determine their physical,
and sometimes their chemical,
properties.
Color is the most easily observed, but least
reliable property of a mineral for
identification.
This is because the color of many minerals
varies with the kind of impurities in the
mineral.
Luster is the way in which a mineral shines in the light.
Streak is the color of the powder left
on a streak plate when a mineral is
rubbed on it.
Streak is much more reliable than
color because, although the color
of a mineral changes, its streak
does not.
Cleavage is the tendency of a mineral
to split in a particular direction.
“Sheety” Cleavage
Feldspars always cleave readily at or near right angles.
Fracture is the tendency of a
mineral to break in directions other
than along crystal faces or cleavage
surfaces.
Conchoidal or shell-like fracture
Fibrous fracture
Hardness is the resistance of a mineral to
being scratched.
The Mohs Hardness Scale is one of the
most effective tool for identifying
minerals.
Additional Properties
Some other properties can also give us clues
about identity:
• Magnetism (Magnetite)
• Glowing under ultraviolet light (Fluorite)
Magnetite
• Salty taste (Halite)
• Smell (Sulfur)
• Reaction to HCl (Calcite)