Minerals Have a Specialized Geologic Definition
The Alma King rhodochrosite
(MnCO3) measures 14 cm x 16.5
cm and is on display at the Denver
Museum of Nature and Science.
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Minerals Must Be Solids
A solid is a state of matter that
can maintain its shape
indefinitely.
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Minerals must be formed by geological processes (freezing from a melt, precipitation
from solution, chemical reaction). Biogenic minerals are a special case formed by
living organisms.
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Minerals Must Have a Crystalline Structure
Most solid materials are crystalline. Solids lacking internal atomic order are called glasses.
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Crystal Lattice
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Crystals
A crystal is a single, continuous piece of crystalline solid typically bounded by
flat crystal faces.
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Atomic Bonding
The geometry of the atomic packing and the
nature of chemical bonding determines the
mineral properties.
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Atomic Bonding
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Atomic Bonding
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Mineral crystals form when a melt solidifies.
Quick cooling results in tiny crystals; slow cooling creates large crystals.
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New crystals can form from an
aqueous solution when dissolved
solids become saturated.
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As crystals grow, they often
encounter other growing
crystals.
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Mineral Destruction
Minerals can be destroyed by melting,
dissolution in aqueous solution, and by
chemical reaction with other minerals,
especially at elevated T and P.
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Mineral Identification
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Mineral Identification
Color is diagnostic of some
minerals (malachite); a poor
indicator for others (quartz).
Malachite
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Mineral Identification
Streak is a property whereby
a mineral leaves a crushed
powder on an unglazed
porcelain plate.
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Mineral Identification
Luster is a property that refers to
the way that a mineral surface
scatters light.
Satin spar gypsum = silky
The two main subdivisions of luster are
metallic and nonmetallic (which has
many subdivisions).
Quartz = vitreous.
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Mineral Identification
Fingernail 2.5
Copper Penny 3.5
Glass - Steel 5.5
Steel File 6.5
1. Talc, Graphite
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Orthoclase
7. Quartz
8. Topaz
9. Corundum
10. Diamond
Hardness is the scratching resistance
of a mineral, which is directly linked to
atomic-bond strength.
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Mineral Identification
Galena—high SG.
Specific gravity (SG) is related to density
(mass/volume). It is approximated by the
“heft” of a sample.
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Cleavage
Cleavage is the tendency for a mineral to
break along lattice planes with weaker
atomic bonds.
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Examples of Cleavage
One direction
Two directions at 90º
Two directions not at 90º
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Examples of Cleavage
Three directions at 90º
Halite
Three directions not
at 90º
Calcite
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Minerals that have no lattice planes of
weakness—bonds equally strong in all
directions—will fracture instead of cleave.
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Minerals are classified by their dominant anion.
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Oxygen bonds with metallic cations to form
important ore mineral oxides.
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Sulfide (S–) combines
with metallic cations
to form many of our
most important metal
ore minerals.
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Sulfates
Gypsum
Many sulfates form via evaporation of seawater.
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Halides
Halides are minerals that have
halogens (F-, Cl-, I-, Br-) as their
dominant anion.
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Fluorite
Carbonates
Carbonates contain the carbonate anion (CO32-).
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Native Elements
Native elements are minerals that occur as a single element.
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Silicates
Oxygen (O)
Silicon (Si)
Aluminum (Al)
Iron (Fe)
Calcium (Ca)
Sodium (Na)
Potassium (K)
Magnesium (Mg)
All others
46.6%
27.7%
8.1%
5.0%
3.6%
2.8%
2.6%
2.1%
1.5%
Potassium feldspar var. amazonite
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Silica Tetrahedron
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Silicates
Quartz crystals and hematite
Silicate minerals are divided into several classes
based upon how the silica tetrahedra are arranged.
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Silicates
Almandine garnet
Silicate minerals with isolated tetrahedra
do not share any oxygens. Instead, they
are bonded together by cations.
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Single Chain Silicates
Pyroxene
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Double-Chain Silicates
Hornblende, an amphibole.
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Sheet Silicates
Muscovite
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Framework Silicates
Orthoclase, a potassium feldspar.
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A Rock Is Coherent
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A Rock Is Natural
Natural
Manufactured
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A Rock Is an Aggregate of Minerals
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Bedrock Is Attached to Earth’s Crust
Natural outcrop
Human-made outcrop
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Rocks Are Classified By Their Origin
Igneous rock forms
from molten material.
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Sedimentary rocks form by
cementation or precipitation.
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Metamorphic rocks form from preexisting rocks due to changes in
temperature and/or pressure.
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