Transcript Minerals of the Earth

Earth Science Notes
MINERALS
Objectives
I can…
 Identify and describe the criteria for crystals
classification
 Explain the concept of the Unit Cell and tell
why it is necessary in explaining mineral
structures
 Determine the identity of minerals based ont
their properties.
Definition of a Mineral
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A mineral is
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naturally occurring,
inorganic,
homogeneous solid with a definite chemical
composition
Has ordered atomic arrangement.
Five parts to this definition
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Naturally occurring – not man made, may be
found on earth, space, or other planets.
Inorganic – minerals are not formed by living
things but by earth processes.
Five parts to this definition
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Homogeneous solid – made up with the same
atoms throughout the mineral.
The Mineral Halite (Sodium Chloride)
Five parts to this definition
Definite chemical composition - atoms must
occur in the same ratios.
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Most minerals are ionic compounds – recall
ionic compounds have a definite ratio of atoms
 aluminum oxide 2:3 ratio
(2 Aluminum atoms to 3 Oxygen atoms)
Five parts to this definition
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Ordered atomic arrangement – must be
crystalline – have repeating units
Unit cell – the most basic component of a
crystal.
Glasses, like obsidian, are not minerals
Orderly Atomic Arrangement
Crystals: solids where atoms are arranged in an
orderly repeating pattern.
Front View of Crystal Lattice
Enlarged 3-D view of Unit Cell
Orderly Atomic Arrangement
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Crystal Lattices – repeated unit cells
Orderly Atomic Arrangement
Crystal Systems – made up of crystal lattices
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Types of crystal systems (also see p 64)
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Cubic
Hexagonal
Monoclinic
Tetragonal
Orthorhombic
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Triclinic
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Orderly Atomic Arrangement
Unit Cell  Crystal Lattice  Crystal System
Mineral Formation
Minerals form as a result of two processes
Magma cooling
 Minerals formed depend on the elements present and
the amount of those elements.
 The size of the mineral crystal depends on the rate at
which the crystal cooled.
Mineral Formation
Minerals form as a result of
two processes
Solutions evaporating
 Solutions have two parts
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Solute – substance being dissolved
Solvent – substance doing the dissolving
With some solutions the solvent (water) can be
evaporated and the solute (salt) dissolved
reappears in crystal form.
Mineral Formation
Solutions evaporating to form minerals: the spotted
lake (kliluk), situated in osoyoos, Canada, contains one of the highest
concentrations of minerals in the world (mainly epsom salts, calcium
and sodium sulphates).
Mineral Classification
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Most mineral groups are based on the elements that
are in the mineral.
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Silicates – vast majority of the earth’s crust.
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Oxides – minerals that have oxygen in them.
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Ex: Pyrite and galena
Halide – … have one of the halogens in them.
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Ex: Hematite and Magnetite
Sulfides – minerals that have sulfur in them.
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Ex: Quartz and Feldspar
Ex: halite (NaCl) and Fluorite
Pure metal elements: Gold, silver, etc
Mineral Identification
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Physical Properties of minerals allow for
accurate identification
Hardness
Luster
Specific Gravity
Streak
Cleavage
Special Properties
Mineral Identification
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Hardness:
determine by
Mohs Scale
HARDNESS
SCALE
INDEX
MINER
AL
1
Talc
2
Gypsum
3
Calcite
4
Fluorite
5
Apatite
6
Orthoclase
7
Quartz
8
Topaz
9
Corundum
10
Diamond
COMMON
OBJECTS
Fingernail
Copper Penny
Glass
Mineral Identification
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Luster: reflecting of light
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The two main types of luster are metallic and
nonmetallic.
Metallic luster
Nonmetallic Luster
Mineral Identification
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Specific Gravity: Specific gravity is the
"heaviness" of a mineral.
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It is defined as a number that expresses the ratio
between the weight of a mineral and the weight of
an equal volume of water. Water has a specific
gravity of 1.
Mineral Identification
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Streak: is the color of the powder left on a
streak plate
Mineral Identification
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Cleavage: is the ability of a mineral to break
along preferred planes.
Fracture: tendency of a
mineral to break along
curved surfaces without a
definite shape
Mineral Identification
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Special Properties of minerals
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Transparency
Magnetism
Tenacity (how tough a mineral is)
Minerals
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Summary
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What makes something a mineral?
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Arrangement and organization of crystal structures
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Unit Cell  lattices  Crystal systems
Formation of Minerals
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Five characteristics
From lava / Solutions
Mineral Identification
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Based on physical properties
Assessment
Can I…
 Identify and describe the criteria for crystals
classification
 Explain the concept of the Unit Cell and tell
why it is necessary in explaining mineral
structures
 Determine the identity of minerals based ont
their properties.