Transcript Geology ch 6 Rocks

CHAPTER 5 ROCKS AND
MINERALS
WHAT IS A
MINERAL???
A naturally formed , inorganic solid
that has a definite crystalline structure.
TWO GROUPS OF MINERALS
• Silicate Minerals – a
mineral that contains
a combination of
silicon, oxygen, and
one or more metals.
• Nonsilicate Minerals –
a mineral that does
not contain
compounds of silicon
and oxygen.
• Examples: Quartz,
Feldspar, and Mica
• Examples: Native
elements,
Carbonates, Halides,
Oxides, Sulfates, and
Sulfides.
IDENTIFYING MINERALS
Using Physical Properties
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Color
Luster
Hardness
Streak
Density
Crystal Shape
Cleavage
Fracture
Special properties
COLOR
• Most obvious way to tell
minerals apart but, most
unreliable because of
impurities found in
minerals.
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Example: Quartz can be:
Pink
Clear
Purple
White
Black
LUSTER
• The quality of light reflected
by a mineral.
• Metallic and nonmetallic are
the types of luster.
Submetallic. In between
• Metallic = shiny
• Nonmetallic = vitreous
(glassy), earthy (dull),
pearly, silky, etc.
HARDNESS
• Resistance of a mineral
to abrasion.
• MOH’S HARDNESS
SCALE
• 1(talc = softest)10(diamond = hardest)
• Scratch test. Scratch
minerals together, one
will scratch the other. If
they don’t, they are the
same hardness.
MOH’S HARDNESS SCALE
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1 Talc
2 Gypsum
3 Calcite
4 Fluorite
5 Apatite
6 Feldspar
7 Quartz
8 Topaz/beryl
9 Corundum
10 Diamond
STREAK
• The color of the
powdered mineral.
• More reliable than
color
• A streak plate is used
to perform this test.
• Streak
plate=Unglazed
porcelain
DENSITY/SPECIFIC GRAVITY
• D=m/v
• Weight of a mineral compared to an equal
volume of water.
• HEFT- Tossing the mineral in your hand.
• If a mineral weighs 3 times as much as an
equal volume of water, it’s specific gravity
is 3.
• Most minerals have a specific gravity of 3.
CRYSTAL SHAPE/FORM
• Internal arrangement
of atoms. (without
constriction)
• 1. Cubic
• 2. Hexagonal
• 3. Orthorhombic
• 4. Monoclinic
• 5. Tetragonal
• 6. Triclinic
CLEAVAGE
• The tendency of a
mineral to break
along smooth definite
surfaces. These are
planes of weak
bonding. Example:
mica
• Number of planes
exhibited and the
angles at which they
meet.
FRACTURE
• Minerals that break
along irregular
surfaces.
• May splinter.
• Smooth curved
surfaces =
Conchoidal Fracture.
“Glasslike”
SPECIAL PROPERTIES
• Magnetite = Magnetic
• Halite = salty (taste)
• Sulfur = smells like rotten
eggs (odor)
• Calcite = fizzes when
HCL is put on it
• Fluorite = Glows under
UV light
• Uraninite = radioactive
• Etc.
CHAPTER 6
• Rock- A collection of one or more
minerals. It can be made of mineral matter
that is not crystalline or organic material.
Rocks are classified into three major
types.
WHAT IS A ROCK ?
A naturally occurring solid mixture
of one or more minerals or organic
matter.
What is the rock cycle?
• The series of processes in which rock
changes forms, changes from one type to
another, is destroyed, and forms again by
geological processes.
THE ROCK CYCLE
Bowen’s reaction series
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The simplified pattern that illustrates the order
in which minerals crystallize from cooling
magma according to their chemical composition
and melting point.
Mafic=Dark colored rock. Contains magnesium
Felsic=Light colored rock. Contains silicon and
feldspar.
Olivine crystallizes first and quartz last.
Bowen’s reaction series
3 TYPES OF ROCKS
IGNEOUS
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Rocks formed from fluid magma within the
Earth.
Classified according to their composition and
texture.
Latin: ignis = fire
Intrusive = Formed deep within the Earth
Extrusive = Formed from lava. (exterior)
Examples: Granite, obsidian, pumice, basalt,
Intrusive/Plutons
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Named after Pluto, the god of the underworld
Examples:
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Sills
Dikes
Laccoliths
Batholiths=largest
4 Basic textures
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1. fine-grained (aphanitic) – small crystals,
cooled quickly. Example= basalt
2. course-grained (phaneritic) – large crystals,
cooled slowly. Example= granite
3. porphyritic – large crystals scattered on a
background on smaller crystals.
4. glassy- no crystals, cooled instantly.
Example= obsidian
Composition of igneous rocks
Felsic
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Describes magma or
igneous rock that is rich in
feldspars and silica and that
is generally light in color.
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Examples: granite, rhyolite,
quartz, feldspar, pumice,
biotite and muscovite mica
Mafic
 Describes magma or
igneous rock that is rich in
magnesium and iron and is
generally dark in color.
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Hornblende, olivine,
pyroxene, basalt, and
gabbro.
Ferromagnesian minerals
Intermediate
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Diorite and Andesite
Intrusive Igneous Rock
structures
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Batholiths-largest
Stocks
Laccoliths
Sills and dikes
Page 133 in textbook. Draw figure 5 into
notebooks.
Extrusive Igneous rock
structures
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Volcano
Volcanic neck
Lava flows
Lava
Tuff- volcanic ash deposit
BELLRINGER
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How are igneous rocks
classified??
SEDIMENTARY
► Rocks
formed by the compacting and
cementing of sediments or by other nonigneous processes at the Earth’s surface.
► Sedimentary rocks are classified into 3 main
categories according to the origin of the
materials from which they were made.
► Define compaction and cementation
CLASTIC(DETRITAL) ROCKS
►A
sedimentary rock formed from fragments of preexisting rocks.
► Example: Sandstone
► Size of particles:
► * Boulder = 256mm+
► * Cobble = 64-255mm
► * Pebble = 2-64mm
► * Sand = .07-2mm
► * Clay and Mud = .06mm
EXAMPLES:
Sandstone
Conglomerate
Shale
Breccia
ORGANIC ROCKS
► Sedimentary
rock formed either directly or
indirectly from material that was once alive.
► Examples : Coal
► Some limestone comes from
shells of sea animals.
CHEMICAL ROCKS
►A
non- clastic sedimentary rock formed by
inorganic processes such as evaporation.
► The particles are too small to see.
► Examples: Limestones (caves)
► Rock Salt (Halite)
Sedimentary rock features
► Stratification-layering
of sedimentary rock.
(beds)
► Cross-beds- slanting layers
► Graded bedding- different sizes and shapes
of sediment settle to different levels.
Usually, largest grains on the bottom and
smallest on the top.
► Reverse grading- smallest on bottom. Large
on top.
► Ripple
marks- caused by action of wind and
water on sand.
► Mud cracks- when muddy deposits dry and
shrink. Can harden into solid rock.
► Fossils – traces of ancient plants and
animals.
► Concretions- a lump of rock that has a
different composition than the main body of
rock.
BELLRINGER
►What
are the three types of
sedimentary rocks?
►How does each type form?
METAMORPHIC ROCKS
• Meta = Change
Morphic = Form
• Rocks changed in form as a result of
chemical reactions, heat, and/or pressure.
• Examples: Gneiss, Schist, Quartzite,
Marble
Metamorphism
• Contact
metamorphism- a
change in the texture,
structure, or chemical
composition of a rock
due to contact with
magma.
• Regional
metamorphism- a
change in texture
,structure, or chemical
composition of a rock
due to changes in
temp and pressure
over a large area,
generally because of
tectonic force.
METAMORPHIC ROCKS
ARE CLASSIFIED IN
TWO WAYS.
Foliated
• Parallel layers or bands.
• 3 Basic textures
– 1. Gnessic- Coarsely foliated
– 2. Schistose- Finely foliated. Along which the
rock splits easily.
– 3. Slaty- Very finely foliated. Parallel planes of
easy splitting.
NON-FOLIATED (Massive)
• Another metamorphic rock, not banded.
• Basic Textures
– 1. Granoblastic- Unfoliated or faintly foliated.
– 2. Hornfelsic- Unfoliated with mineral grains
that are completely microscopic; breaks
sharply into angles.
Metamorphic rocks
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Granite= Gneiss
Sandstone= Quartzite
Bituminous coal= Anthracite coal
Shale= Slate
Limestone= Marble