II Properties of Minerals'

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ROCKS MINERALS
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What is a mineral?

• a naturally occurring,
• inorganic,
• crystalline
• solid
• with a definite chemical composition.

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Definition of a mineral has 5 parts
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1. naturally occurring

• formed in nature and is not made by man.
• Ex) concrete and glass are not minerals.

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2. Inorganic

• it has not been made by or composed of life
  forms.
• Fossil fuels and pearl are not minerals.

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3. Crystalline

• its atoms have a specific arrangement (crystal
  structure).

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CRYSTAL STRUCTURE

• The pattern or arrangement of atoms that
  characterizes each mineral
• also called atomic structure.

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4. solid
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5. definite chemical composition.

• the types and ratio of elements that make up the
  mineral remains constant.
• Ex) H2O 2 hydrogen for each oxygen

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MINERAL COMPOSITON OF THE EARTHS CRUST

• see ESRT page 11

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• 8 elements account for 99 of the Earths crust.
• Two most common elements by mass are
• oxygen
• silicon
• Two most common elements by volume are
• oxygen
• potassium

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PROPERTIES OF MINERALS
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Physical properties of a mineral are determined
by either.

• 1 - chemical composition.
• color
• luster
• streak
• 2 - crystal structure (arrangement of atoms)
• hardness
• cleavage
• crystal form

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PROPERTIES CAUSED BY CHEMICAL COMPOSITION
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1- COLOR

• Color is not useful when identifying a mineral.
• There are three reasons why..

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1)Many different minerals have similar colors.
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2) One mineral may occur in different colors.

• Pure quartz is colorless or white. A small
  amount of iron give quartz a purple color. A
  small amount of titanium results in pink quartz.

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3) Some minerals change color when exposed to
air.

• In air, the brass-yellow color of chalcopyrite
  tarnished to bronze.

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2 - LUSTER

• the way a mineral looks or shines in reflected
  light.

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There are two (major) types of luster.

• 1) Metallic
• shines like polished metal.
• 2) Non-metallic
• does not shine like polished metal.

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3 - STREAK

• the color of the powder of a mineral.
• it is determined by rubbing the mineral on a
  streak plate.

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The streak of a metallic mineral is

• ...dark and distinct.

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The streak of a nonmetallic mineral is ...

• colorless or white.
• not very useful..

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PROPERTIES CAUSED BY CRYSTAL STRUCTURE
(arrangement of the atoms)
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1 - HARDNESS

• the resistance of a mineral to being scratched.
• usually measured by using Mohs hardness scale.

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Mohs scale?

• measures the hardness of any common material.
• scale goes from 1 to 10.
• The hardest mineral (10) is
• Diamond
• The softest mineral (1) is
• Talc

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if fingernail scratches
if it scratches glass plate
m gt 5.5
m lt 2.5
2.5 5.5
2.5
5.5
1
10
fingernail
glass plate
Hardness Scale
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2 - CLEAVAGE

• when a mineral breaks, smooth to semi-smooth
  parallel surfaces are produced.

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FRACTURE

• the way in which a mineral breaks producing an
  uneven breaking surface.

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3 - CRYSTAL SHAPE (form)

• the outward shape of a mineral specimen that
  reflects the internal atomic structure
• also called crystal form.

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Special Properties
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1) Acid Test

• Calcite will react with hydrochloric acid.
• a drop of acid will fizz.
• the acid will dissolve the calcite.

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2) magnetic

• a magnet will be attracted to the mineral.

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3) taste

• halite has a salty taste.

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4) fluorescence

• these minerals will glow while under ultraviolet
  light.

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5) radioactive

• these minerals give off subatomic particles that
  will activate a Geiger counter.

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6) double refraction

• this causes two images to be seen when the object
  is viewed through the mineral specimen.

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• The two most abundant elements by mass in Earths
  crust are oxygen and
• (1) potassium (3) nitrogen
• (2) hydrogen (4) silicon

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• 2) The internal atomic structure of a mineral
  most likely determines the minerals
• (1) color, streak, and age
• (2) origin, exposure, and fracture
• (3) size, location, and luster
• (4) hardness, cleavage, and crystal shape

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• Base your answers to questions 3 and 4 on the
  diagram below, which shows three minerals with
  three different physical tests, A, B, and C,
  being performed on them.
• 3) Which sequence correctly matches each test, A,
  B, and C, with the mineral property tested?
• Acleavage Bstreak
• Chardness
• (2) Acleavage Bhardness
• Cstreak
• (3) Astreak Bcleavage
• Chardness
• (4) Astreak Bhardness
• Ccleavage

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• Base your answers to questions 3 and 4 on the
  diagram below, which shows three minerals with
  three different physical tests, A, B, and C,
  being performed on them.
• 4) The results of all three physical tests shown
  are most useful for determining the
• rate of weathering of
• the minerals
• (2) identity of the minerals
• (3) environment where the
• minerals formed
• (4) geologic period when the
• minerals formed

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• 5) A human fingernail has a hardness of
  approximately 2.5. Which two minerals are softer
  than a human fingernail?
• calcite and halite
• (2) graphite and talc
• (3) sulfur and fluorite
• (4) pyrite and magnetite

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• 6) An unidentified mineral that is softer than
  calcite exhibits a metallic luster and cubic
  cleavage. This mineral most likely is
• (1) galena (3) halite
• (2) pyrite (4) pyroxene

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ROCKS AND MINERALS
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Rock

• a group of minerals bound together.

granite
coquina
breccia
porphyry
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Rocks are identified by their

• 1 texture
• the size, shape and arrangement of the mineral
  grains that make up the rock.
• 2 composition
• (crystals, sediments, fossils).

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There are three types of rocks(Rocks are
classified according to how they were produced)

• 1 Igneous
• cooling of molten rock material.
• 2 Sedimentary
• mostly sediments that have been cemented
  together.
• 3 Metamorphic
• Rocks that have been altered by heat and or
  pressure.

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• IGNEOUS ROCKS
• Using ESRT worksheet.p.6

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Formation of Igneous rocks
Reference Tables p.6
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Igneous Rocks

• form when a magma or lava cools.
• minerals form distinct, interlocking grains.

Pumice
Andesite
Obsidian
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• Magma
• hot molten rock beneath the Earths surface.

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Pahoehoe
Aa flow
Ropy pahoehoe

• Lava
• magma that reaches the Earths surface.

pahoehoe flow, Kilauea Volcano, Hawaii
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Igneous rocks form in two ways

• 1. Intrusive (aka Plutonic) rocks.
• form deep underground.
• Magma cools slowly.
• large (gt1mm) mineral grains.
• Coarse - grained texture.

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• 2. Extrusive (aka Volcanic) rocks.
• forms at or near Earths surface.
• Lava cools quickly.
• little time for mineral grains to form small
  grains (lt1mm).
• Fine - grained or glassy texture.

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There are two kinds of magma

• 1 - Felsic Magma.
• silica rich (SiO2).
• Al rich.
• magma is thick and slow flowing.
• Forms light-colored minerals (quartz, K-spar)

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• 2 - Mafic Magma.
• lower silica content.
• Ca, Fe, Mg rich.
• Magma is hotter, thinner, and more fluid.
• Forms dark-colored minerals (hornblende,
  pyroxene, Na-plag)

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Common Igneous Rocks
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1 - Obsidian

• volcanic glass (granite family).
• usually dark in color.
• conchoidal (shell-like) fracture.

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2 - Pumice

• felsic lava that hardened while steam and gases
  were still escaping.
• has many air holes in it.
• sometimes it will float.

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3 - Scoria

• like pumice it is full of holes,
• scoria is made of denser minerals (it won't float)

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Identifying Igneous Rocks
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1)Determine the shade of the rock.

• Light shade (remember pink and red are light in
  shade).
• Dark shade (green is dark shade).
• Intermediate (something between dark and light).

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2) Determine the texture of the rock.

• Coarse - you can see the individual mineral
  grains.

GABBRO
GRANITE
DIORITE
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• Fine - you can not see the individual mineral
  grains.

ANDESITE
RHYOLITE
BASALT
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• Porphyritic - contains both coarse and fine
  grains.

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• Glassy (obsidian)

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• Vesicular - has holes in it (scoria, pumice)

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3) Use the Earth Science Reference Tables to
determine the rocks name.
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• SEDIMENTARY ROCKS
• Using ESRT worksheet.p.7

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Sedimentary rocks

• are rocks that form from an accumulation of
  sediments and/or organic material.

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There are three types of Sedimentary rocks

• Clastic
• sediments
• Chemical
• precipitates and evaporates
• Organic
• biologic origin

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1 - CLASTIC SEDIMENTARY ROCKS

• most sedimentary rocks are clastic.
• clast - solid sediments weathered from other
  rocks.

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sediment

• particles or materials formed by the weathering
  and erosion of rocks or organic materials.

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Clasts vary in size from pebbles to microscopic
flakes of clay.
Reference Tables page 6
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Clasts can be moved (transported) by

• wind
• waves
• running water, and
• glaciers.

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Running water

• collects and moves the greatest amount of
  sediment.
• as the clasts bump into one another (abrasion),
  their edges become rounded and smooth.
• When the velocity of a stream decreases the
  materials are deposited (dropped).
• this occurs when a river flows into a lake or
  ocean.

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Mississippi river delta
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• During deposition, the sediments become sorted .
• (sorted - grouped according to particle size)
• Large particles are deposited first.
• (close to the shore).
• Fine particles are deposited last.
• (far from the shore).

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river
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coarse
river
pebbles
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coarse
river
pebbles
Conglomerate
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coarse
river
pebbles
Conglomerate
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sands
coarse
river
pebbles
Conglomerate
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sands
coarse
river
pebbles
Conglomerate
Sandstone
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sands
coarse
river
pebbles
Conglomerate
Sandstone
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sands
coarse
river
clays
pebbles
Conglomerate
Sandstone
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sands
coarse
river
clays
pebbles
Conglomerate
Sandstone
Shale
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Formation of Sedimentary rocks
Reference Tables p.6
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Method of formation

• Existing rock is broken down into sediments by
  weathering and erosion.
• Sediments are transported to another location.
• Sediments are deposited, one layer on top of
  another.
• Pressure from overlying sediments compresses and
  compacts the sediments which may cause them to
  stick together.
• Dissolved minerals may settle into the spaces
  between the clasts and cement the materials
  together.

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Examples of Clastic Rocks

• (examples shale, sandstone, conglomerate).

conglomerate
shale
sandstone
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2 CHEMICAL SEDIMENTARY ROCKS

• liquid water contains dissolved minerals.
• as the water evaporates, the minerals
  precipitate (drop out of the water) and form a
  mass of mineral crystals.

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Examples of Chemical rocks.

• (examples rock salt, gypsum).

Rock salt
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3 ORGANIC SEDIMENTARY ROCKS

• organic means anything related to living
  organisms.
• any rock made by living organisms.
• any rock mostly composed of material from life
  forms.
• may contain fossils.

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Examples of Organic rocks.

• (examples coal, and limestone)

coquina
coal
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fossil

• any evidence of former life
• remains, impressions, footprints.

ammonite
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• 1) Which rock was organically formed and
  sometimes contains fossilized plant impressions?
• rock gypsum (2) breccia
• (3) phyllite (4) coal

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• 2) Which processes most likely formed the shale
  bedrock found near Ithaca, New York?
• uplift and solidification
• burial and compaction
• (3) heat and pressure
• (4) melting and recrystallization

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• 3) Dolostone is classified as which type of rock?
• land-derived sedimentary rock
• (2) chemically formed sedimentary rock
• (3) foliated metamorphic rock
• (4) nonfoliated metamorphic rock

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• 4) Which cross section best shows the pattern of
  sediments deposited by the stream as it enters
  the ocean near point Z?

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• 5) Most of the rocks shown were formed by
• volcanic eruptions and crystallization
• (2) compaction and/or cementation
• (3) heat and pressure
• (4) melting and/or solidification

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• 6) Which two rocks are composed primarily of
  quartz, feldspar, and clay minerals?
• (1) rock salt and conglomerate
• (2) rock salt and breccia
• (3) sandstone and shale
• (4) sandstone and limestone

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• Which table shows the rocks correctly classified
  by texture?

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METAMORPHIC ROCKS

• Using the Earth Science Reference Tables p. 7

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METAMORPHIC ROCKS

• rocks that form from changes in previously
  existing rocks due to heat and or pressure.

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Formation of Metamorphic rocks
Reference Tables p.6
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Effects of metamorphism on rocks

• pressure squeezes the grains closer together
  making the rock more dense and less porous.
• heat and chemicals rearrange the particles.
• minerals may recrystallize and/or new minerals
  may form.
• pressure may cause distorted structure (the
  curving and folding of the foliation within the
  rock).

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Foliation - a layered arrangement (minerals are
aligned in layers)

• some metamorphic rocks are foliated.
• other metamorphic
• rocks may be banded.
• (colored bands banding).

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There are two types of Metamorphism

• Regional
• Contact

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Regional metamorphism

• large areas of rock are exposed to intense heat
  and pressure.
• occurs during mountain building, folding and
  faulting.

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Contact Metamorphism

• occurs when hot magma forces its way into
  surrounding rock.
• the heat of the magma bakes the rock that are in
  contact with it.
• the area affected is much less than regional
  metamorphism(usually less than 100 m).
• the changes in the rock are less dramatic and
  foliation usually does not occur.

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THE ROCK CYCLE(see ESRT)

• is used to show how the rock types are related.
• it also shows the process that produces each rock
  type.
• any rock type can change into any other rock type.

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ROCK TYPES

• Rock
• a group of minerals bound together.

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Rocks are identified by their

• 1 texture
• the size, shape and arrangement of the mineral
  grains that make up the rock.
• 2 composition
• (crystals, sediments, fossils).

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There are three types of rocks

• Igneous.
• Sedimentary.
• Metamorphic.

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Sedimentary Rock

• formed by the hardening and cementing of layers
  of sediments.
• Characteristics
• bedding or layering of sediments.
• rounded grains, clasts, and fragments.
• fossils.
• cemented sediments with visible pore spaces.
• fragments of other rocks.

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Igneous Rocks

• form from the cooling and solidification of
  liquid rock.
• Characteristics
• crystalline texture.
• intergrown mineral crystals.
• random arrangement.
• polyminerallic composition.
• glassy texture.
• rounded gas pores or spaces.

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Metamorphic Rock

• preexisting rocks are changed by heat and
  pressure.
• Characteristics
• polyminerallic composition.
• interconnected minerals.
• layering (foliation)slaty, schistose or gneissic
  formation (banding)
• distorted or wavy rock structure.
• stretched pebbles.
• high percentage of mica minerals.

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