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Lab #4:Lab #4:
Minerals: Building Minerals: Building
Blocks of RocksBlocks of Rocks
Minerals: Building Blocks Minerals: Building Blocks
of Rocksof Rocks
By definition a By definition a mineralmineral is/hasis/has
Naturally occurringNaturally occurring
Inorganic solidInorganic solid
Ordered internal molecular structureOrdered internal molecular structure
Definite chemical compositionDefinite chemical composition
RockRock
A solid aggregate of mineralsA solid aggregate of minerals
Composition and Structure Composition and Structure
of Mineralsof Minerals
ElementsElements
Basic building blocks of mineralsBasic building blocks of minerals
Over 100 are known (92 naturally Over 100 are known (92 naturally
occurring)occurring)
AtomsAtoms
Smallest particles of matterSmallest particles of matter
Retain all the characteristics of an Retain all the characteristics of an
elementelement
2
Composition and Structure Composition and Structure
of Mineralsof Minerals
Atomic structureAtomic structure
Central region called the Central region called the nucleusnucleus
�� Consists of Consists of protonsprotons (+ charges) and (+ charges) and
neutronsneutrons ((-- charges)charges)
ElectronsElectrons
�� Negatively charged particles that surround Negatively charged particles that surround
the nucleusthe nucleus
�� Located in discrete energy levels called Located in discrete energy levels called
shellsshells
Structure of an AtomStructure of an Atom
Figure 1.5 A
Composition and Structure of Composition and Structure of
MineralsMinerals
Chemical bondingChemical bonding
Formation of a compound by Formation of a compound by
combining two or more elementscombining two or more elements
Atoms gain or lose outermost Atoms gain or lose outermost
electrons to form electrons to form ionsions
Oppositely charged ions attract one Oppositely charged ions attract one
another to produce a neutral another to produce a neutral
chemical compoundchemical compound
3
Composition and Structure of Composition and Structure of
MineralsMinerals
Isotopes and radioactive decayIsotopes and radioactive decay
Mass numberMass number = sum of neutrons + = sum of neutrons +
protons in an atomprotons in an atom
IsotopeIsotope = atom that exhibits variation = atom that exhibits variation
in its mass numberin its mass number
Unstable isotopes emit particles and Unstable isotopes emit particles and
energy in a process known as energy in a process known as
radioactive decayradioactive decay
Physical Properties Physical Properties
of Mineralsof Minerals
Crystal formCrystal form
External expression of a mineralExternal expression of a mineral’’s s
internal structureinternal structure
Often interrupted due to competition Often interrupted due to competition
for space and rapid loss of heatfor space and rapid loss of heat
A Garnet CrystalA Garnet Crystal
4
Cubic Crystals of PyriteCubic Crystals of Pyrite
Figure 1.7 A
Physical Properties Physical Properties
of Mineralsof Minerals
LusterLuster
Appearance of a mineral in reflected Appearance of a mineral in reflected
lightlight
Two basic categoriesTwo basic categories
�� MetallicMetallic
�� NonmetallicNonmetallic
Other descriptive terms include Other descriptive terms include
vitreous, silky, or earthyvitreous, silky, or earthy
Galena (PbS) Displays Metallic Galena (PbS) Displays Metallic
LusterLuster
Figure 1.13
5
Physical Properties Physical Properties
of Mineralsof Minerals
ColorColor
Generally unreliable for mineral Generally unreliable for mineral
identificationidentification
Often highly variable due to slight Often highly variable due to slight
changes in mineral chemistrychanges in mineral chemistry
Exotic colorations of certain minerals Exotic colorations of certain minerals
produce gemstonesproduce gemstones
Quartz (SiOQuartz (SiO22) Exhibits ) Exhibits
a Variety of Colorsa Variety of Colors
Physical Properties Physical Properties
of Mineralsof Minerals
StreakStreak
Color of a mineral in its powdered Color of a mineral in its powdered
formform
HardnessHardness
Resistance of a mineral to abrasion Resistance of a mineral to abrasion
or scratchingor scratching
All minerals are compared to a All minerals are compared to a
standard scale called the standard scale called the Mohs scale Mohs scale
of hardnessof hardness
6
Streak Is Obtained on an Streak Is Obtained on an
Unglazed Porcelain PlateUnglazed Porcelain Plate
Figure 1.8
Mohs Scale
of
Hardness
Figure 1.9
Physical Properties Physical Properties
of Mineralsof Minerals
CleavageCleavage
Tendency to break along planes of Tendency to break along planes of
weak bondingweak bonding
Produces flat, shiny surfacesProduces flat, shiny surfaces
Described by resulting geometric Described by resulting geometric
shapesshapes
�� Number of planesNumber of planes
�� Angles between adjacent planesAngles between adjacent planes
7
Fluorite, Halite, and Calcite All Fluorite, Halite, and Calcite All
Exhibit Perfect CleavageExhibit Perfect Cleavage
Figure 1.11
Physical Properties Physical Properties
of Mineralsof Minerals
FractureFracture
Absence of cleavage when a mineral Absence of cleavage when a mineral
is brokenis broken
Specific GravitySpecific Gravity
Weight of a mineral/weight of an Weight of a mineral/weight of an
equal volume of waterequal volume of water
Average value = 2.5 Average value = 2.5 –– 3.03.0
Conchoidal FractureConchoidal Fracture
Figure 1.12
8
Physical Properties Physical Properties
of Mineralsof Minerals
Other propertiesOther properties
MagnetismMagnetism
Reaction to hydrochloric acidReaction to hydrochloric acid
MalleabilityMalleability
Double refractionDouble refraction
TasteTaste
SmellSmell
ElasticityElasticity
Mineral GroupsMineral Groups
Nearly 4000 minerals have been Nearly 4000 minerals have been namednamed
RockRock--forming mineralsforming minerals
Common minerals that make up most Common minerals that make up most of the rocks of Earthof the rocks of Earth’’s crusts crust
Only a few dozen membersOnly a few dozen members
Composed mainly of the 8 elements Composed mainly of the 8 elements that make up over 98% of the that make up over 98% of the continental crustcontinental crust
Elemental AbundancesElemental Abundances
in Continental Crustin Continental Crust
Figure 1.14
9
Mineral GroupsMineral Groups
SilicatesSilicates
Most important mineral groupMost important mineral group
�� Comprise most rockComprise most rock--forming mineralsforming minerals
�� Very abundant due to large % of silicon Very abundant due to large % of silicon
and oxygen in Earthand oxygen in Earth’’s crusts crust
SiliconSilicon--oxygen tetrahedronoxygen tetrahedron
�� Fundamental building blockFundamental building block
�� Four oxygen ions surrounding a much Four oxygen ions surrounding a much
smaller silicon ion smaller silicon ion
Two
Illustrations
of the
Si–O
Tetrahedron
Figure 1.15
Mineral GroupsMineral Groups
Common silicate mineralsCommon silicate minerals
Feldspar groupFeldspar group
�� Most common mineral groupMost common mineral group
QuartzQuartz
�� Only common silicate composed entirely Only common silicate composed entirely
of oxygen and siliconof oxygen and silicon
10
Potassium FeldsparPotassium Feldspar
Figure 1.17
Mineral GroupsMineral Groups
Important nonsilicate mineralsImportant nonsilicate minerals
Comprise only 8% of EarthComprise only 8% of Earth’’s crusts crust
Often occur as constituents in Often occur as constituents in
sedimentary rockssedimentary rocks
Table 1.1
11
Mineral GroupsMineral Groups
Important nonsilicate mineralsImportant nonsilicate minerals
CarbonatesCarbonates
�� Primary constituents in limestone and Primary constituents in limestone and
marblemarble
�� Limestone is used commercially for Limestone is used commercially for
road paving, building stone, and as the road paving, building stone, and as the
main ingredient in Portland cementmain ingredient in Portland cement
Mineral GroupsMineral Groups
Important nonsilicate mineralsImportant nonsilicate minerals
HaliteHalite and and gypsumgypsum
�� Both are commonly found in thick layersBoth are commonly found in thick layers
�� Like limestone, both halite and gypsum Like limestone, both halite and gypsum
are important nonmetallic resourcesare important nonmetallic resources
Mineral GroupsMineral Groups
Important nonsilicate mineralsImportant nonsilicate minerals
A number of other minerals have A number of other minerals have
economic valueeconomic value
ExamplesExamples
�� HematiteHematite (oxide mined for iron ore)(oxide mined for iron ore)
�� SphaleriteSphalerite (sulfide mined for zinc ore)(sulfide mined for zinc ore)
�� GalenaGalena (lead)(lead)
�� Native copperNative copper (native element mined for (native element mined for
copper)copper)
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Native CopperNative Copper
Complete Lab #4:Complete Lab #4:
MineralsMinerals