Transcript Minerals and Rocks - Ms. Lewis and Mr. Shumaker

Properties of Minerals
Minerals must :
1.) occur naturally, formed by
nature, not by man
2.) form from an inorganic processfrom things that were never living
3.) be solid- tightly packed particles
4.) have a crystalline structure-the
particles line up in a repeating pattern,
flat sides called faces meet at sharp
edges and corners.
5.) have a definite chemical combination- only certain
elements in definite proportions.
Minerals, Compounds and Elements
• Almost all minerals are compounds
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Different minerals have different combinations of elements
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Compound-combination of two or more elements, compound has
different properties than either element
quartz-one atom of Si for every two atoms
of O (SiO2)
Garnet- Si3O12, BUT garnets also contain
other elements in set ratios
Some elements occur in nature in pure
form and not part of a compound
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ex. Cu, Ag, Au
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Almost all pure, solid elements are metals
Mineral Identification
• Each mineral has characteristic properties that can be used
to identify it
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Color-both A & B are gold in color,
one is the mineral gold, the other
is the mineral pyrite (FeS2)
Streak-color of minerals powder, streak color and mineral
color are often not the same, unlike color, streak never
varies for elements that are the same
Luster-how light is reflected from a minerals surface;
metallic, glassy, earthy (dull), silky, waxy, pearly
Copper-metallic Calcite-glassy
Kaolinite-dull
Serpentine Vein-Silky Chalcedony- waxy
Bornite-Pearly
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Hardness-developed by Friedrich Moh, used to rank hardness of
minerals from 1-10
Moh's Hardness Scale
Scratch test done to determine
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A mineral can scratch any other
mineral that is softer than itself,
but will be scratched by a mineral
that is harder than it
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fingernail (hardness = 2.5)
copper penny (hardness = 3)
Iron nail (hardness = 4)
glass plate or steel knife (hardness = 5.5)
steel file (hardness = 6.5)
Ceramic tile (hardness = 7)
Hardness
Mineral
Description
1
Talc
Fingernail
scratches it easily.
2
Gypsum
Fingernail
scratches it.
3
Calcite
Copper penny
scratches it.
4
Fluorite
Steel knife
scratches it easily.
5
Apatite
Steel knife
scratches it.
Feldspar
Steel knife does
not scratch it
easily, but
scratches glass.
7
Quartz
Hardest common
mineral. It
scratches steel and
glass easily.
8
Topaz
Harder than any
common mineral.
9
Corundum
It scratches Topaz.
10
Diamond
It is the hardest of
all minerals.
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Density-mass in a given space, mineral size does not matter,
density will always be the same for that specific mineral
Density of quartz 2.5 g/cm3, diamond 3.5 g/cm3
Density = mass/volume
mass is found using triple beam balance
volume is found using water displacement in graduated cylinder
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• Crystal Structure-created due to repeating pattern of atoms in
mineral
All crystals in a mineral
have the same structure, used on
small minerals
• Crystals classified based on
number of faces (sides) and
angles at which the faces meet
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Cleavage and Fracture
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Cleavage- a minerals ability to split easily along flat surfaces
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Depends on how atoms are arranged, lines up = splitting in one
direction
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Ex. mica
Fracture- the way a mineral looks when it breaks apart in an irregular
way
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Most minerals exhibit fracturing
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Ex. Quartz (curved, shell like
surfaces)
Special Properties
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Bending of light to show double images
Electrical conductors
Glow under UV light
Magnetic
Mineral Lab Samples
How do minerals form
Geode-rounded hollow rock that is usually lined with crystals
crystals form in geode when water containing dissolved
minerals seeps into the cracks or hollow of a rock, then the
mineral slowly crystalizes
Crystallization-the process where atoms are arranged to
form a crystal structure
Minerals form three ways
1.) organic processes
2.) from materials dissolved in solutions
3.) as magma and lava cools
Mineral Formation
1. Organic Process
All minerals form by inorganic processes, but some form from organic processes as
well
Ex. ocean animals (clams and corals) produce shells and skeletons made out
of calcite
2. Minerals from Solution
Elements and compounds that form minerals can be dissolved in water to form
solutions
solution
1.) Minerals form by evaporation-halite, gypsum, calcite
2.) Minerals from hot water solutions- hot water dissolves elements and compounds
and as water cools, crystallization occurs
ex quartz, silver, gold, selenite
Veins- A narrow deposit of a mineral that is sharply different from the surrounding
rock
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When elements and compounds leave a solution, crystallization occurs
3. Minerals from magma and lava
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Hot magma cools inside the crust or as lava hardens on the surface—this
causes crystals to form
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Minerals from magma = quartz, feldspar, tourmaline and mica
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Minerals from lava = leucite, olivine
--magma and lava are rich in oxygen and silicon, otherwise known as silicates
silicates make up majority of earth’s crust
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Size of crystals depend on:
1.) rate that magma cools
magma deep in earth cools slowly ---large crystals
lava at surface cools quickly—small crystals
2.) amount of gas in magma
3.) chemical composition
Classifying Rocks
Geologists study rocks by observing the rocks:
1.) Composition and Color
2.) Texture
3.) Origin
Composition and Color
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Rocks are made of minerals and other mixtures—some have one mineral,
others have several
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Rock-forming minerals- 20 minerals that make up Earth’s crust
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Color provides clues to the mineral composition
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Granite = light colored rock due to composition-quartz, feldspar, mica, and
hornblende (high in silicates), visible grains
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Basalt = dark-colored, low silica, mineral crystals too small to be seen
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Like with minerals, color alone cannot be used to identify rocks
Texture
Grains-The particles of minerals or other rocks that give
rock its texture
Texture-the look and feel of a rocks surface
Grain Size
-Large and easy to see = coarse grain
*diorite-igneous
-Small, only seen with a microscope = fine
grained
*slate-metamorphic
Grain Shape-due to shape of mineral crystals or other pieces of rock that make up larger rock
-rounded (conglomerate-sedimentary) vs. jagged (breccia-sedimentary)
Grain Pattern
-foliated (banded) = grains in flat layers or
swirls of colored bands
ex. Gneiss-metamorphic
-non foliated (no banding) = no visible
patterns
ex. Quartzite-metamorphic
Origin
Using color, mineral composition, and texture rocks are classified according to their origin
Sedimentary-small particles of rocks or the remains of plants and animals are pressed
and cemented together
--forms in layers buried below the surface
CLASTIC Sedimentary Rocks- made up of pieces
• Grain size smallest to largest- clay, silt, sand
• Grains larger that 2mm = pebbles
• Shale is a rock made mostly of clay, breaks apart
in large flat sections.
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Siltstone is made up of silt-sized grains
Sandstone is made of sand-sized particles
Conglomerate is made of pebbles surrounded
by a matrix of sand or mud.
BIOLOGICAL Sedimentary Rocks- large numbers of living things die, pile up, and are compressed
and cemented to form rock.
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Coal
• Limestone -many fossils and is made of calcium carbonate &/or microscopic shells.
Igneous-cooling of magma or lava
Intrusive-magma, cools slowly, large, coarse grained texture
Extrusive –lava, cools quickly, small grain, fine-grained or even glassy
texture,
--Hot gas bubbles are often trapped in the quenched lava, forming a
bubbly texture
Metamorphic- forms when rock is changed due to heat or pressure or by
chemical reactions, forms deep under ground
• Metamorphic rocks are often squished, smeared out, and folded.
• Metamorphic rocks are the least common of the 3 kinds of rocks.
• Metamorphic rocks are igneous or sedimentary rocks that have been
transformed by great heat or pressure.
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Despite these uncomfortable conditions, metamorphic rocks do not get hot
enough to melt
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Granite (igneous)
Shale (sedimentary)
Limestone (sedimentary)
Sandstone (sedimentary)
Gneiss
Slate
Marble
Quartzite
Rock Type
Formed by
Identifying
characteristics
Examples
Igneous
cooling of magma or lava
Grain size—course
(intrusive) vs. fine
(extrusive)
Granite and Dioritecourse
Obsidian and Pumicefine
Sedimentary
small particles of rocks or
the remains of plants and
animals are pressed and
cemented together
Grain Shape—
rounded vs. jagged
Conglomeraterounded
Particle size (clay,
silt, sand)
Breccia-jagged
Shale, Siltstone,
Sandstone
Metamorphic
forms when rock is changed
due to heat or pressure or
by chemical reactions,
forms deep under ground
Grain patternbanded vs. non
banded
Gneiss and Slatefoliated (banded)
Marble and Quartzitenon foliated (non
banded)
Rock cycle- Forces inside Earth and at the surface produce a slow
cycle that builds, destroys and changes the rocks in the crust from
one kind to another
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There are many pathways in the rock cycle
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Here is one example
Stone Mountain (Atlanta, GA) made of granite (igneous rock), formed
millions of years ago as magma cooled beneath Earth’s surface
 Mountain building pushed rock to and above surface
 Weathering and erosion wear away granite forming sand
 Streams carry sand to ocean
 Sand piles up and becomes compacted forming sandstone (sedimentary
rock)
 Pressure compacts rock, texture changes from gritty to smooth
 After millions of years, sandstone changes to quartzite (metamorphic
rock)
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Plate tectonics drives the rock cycle by forming magma (which forms
igneous rock)
Where plates move apart-igneous rock formed
Where oceanic plate subducts-igneous rock forms
(volcano made of igneous rock)
Collision of continental plates
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pushes rock deep, melting forming igneous rock
Push up a mountain range, weathering and erosion = sedimentary rock
Push rock deep beneath surface, exposing to high heat and pressure =
metamorphic rock
Conservation of matter
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Constructive and Destructive Forces build and destroy Earth
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As rock moves through the rock cycle, material is not lost or gained
The Rock Cycle
Through melting, weathering and erosion, and heat and pressure,
the rock cycle constantly changes rocks from one type into another type.