Transcript Minerals - Choteau

Minerals
Chapter 3
What is a Mineral?
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Mineral
Characteristics
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Naturally occurring
Inorganic
Solid
Definite chemical composition
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Either elements or compounds
Have orderly arrangements of
atoms
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Crystalline/Set atomic pattern
The Structure of Minerals
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Crystals
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Solids in which the atoms are
arranged in orderly, repeating
patterns.
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Minerals are classified into six
major crystal systems according to
their crystal structures:
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Hexagonal
Cubic
Tetragonal
Orthorhombic
Monoclinic
Triclinic
The Structure of Minerals
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Formation of
Crystals:
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From the cooling and
solidification of magma
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The type and amounts of elements
present in the magma partly
determine which minerals will form.
How rapidly the magma cools
determines the size of the crystals.
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Slow – large
Fast – little
From the evaporation of a
solution or the supersaturating
of a solution
Mineral Compositions and Groups
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Mineral
Classification
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2 Main Groups:
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Silicates
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Minerals that contain silicon and oxygen
Contain most of the common rockforming minerals
Nonsilicates
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Do not contain silicon
Mineral Compositions and Groups
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Mineral
Amounts:
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About 4,000 different mineral
are found on Earth.
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90 elements occur naturally in
the crust of the Earth.
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Only a few dozen of these minerals
are common.
~98% of the crust is made of only
eight elements.
Silicon and Oxygen are two of
the most abundant elements
found in Earth’s crust.
Identification of Minerals
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Hardness
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A measure of how easily a
mineral can be scratched
Measured on a scale of 1 to 10
called the Mohs Scale.
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10 = hardest, diamond
1 = softest, talc
Iron nail = 4.5
Fingernail = 2.5
Identification of Minerals
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Luster
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The way a mineral reflects light.
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Metallic or nonmetallic
Identification of Minerals
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Specific
Gravity
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Ratio of the weight of the
mineral with the weight of an
equal volume of water.
Specific gravity of minerals can
be roughly relatively tested
using heft.
Identification of Minerals
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Streak
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Color of a mineral in a powder
form
Found by rubbing the mineral
across a porcelain streak plate
Identification of Minerals
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Cleavage
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Mineral breaks along smooth,
flat surfaces
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Due to the atomic arrangement of
the mineral
Identification of Minerals
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Fracture
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Fracture
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Mineral breaks along rough,
uneven, or jagged surfaces.
Identification of Minerals
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Color and
Appearance
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Color and Appearance
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Highly unreliable.
Identification of Minerals
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Other
Properties
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Other properties
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Magnetic
Optics
Chemical reactions
Gems
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Properties of
Gems
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Gemstones are highly prized
minerals because they are rare
and beautiful.
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Most gems are special varieties of
a particular mineral.
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Clearer, brighter, or more colorful
Have a slightly different chemical
formula:
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Amethysts are quartz with a trace
amount of iron.
Have a better crystal structure.
Gems
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Important
Gems
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Cullinan Diamond
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Largest uncut diamond discovered
Found in South Africa in 1905
3,106.75 carats (621 g)
Cut into 9 main stones and 96 smaller stones
Largest of these, the Great Star of Africa
(530.20 carats) is part of the British crown
jewels.
Hope Diamond
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Purchased by Henry Philip Hope around 1830.
45.52 carats (9 g)
All Hope’s family plus a later owner suffered
misfortune.
Currently on display in the Smithsonian.
Gems
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Useful Gems
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Diamonds
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Rubies
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Used as industrial abrasives and
cutting tools
Produce certain types of laser light
Quartz
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Used in timepieces and electronics
Useful Elements in Minerals
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Ores
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A mineral or rock that contains a
useful substance that can be
mined at a profit
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Examples:
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Iron is found in the ores hematite and
magnetite
Aluminum is found in the ore bauxite
Useful Elements in Minerals
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Extracting
Elements
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Refining
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Wanted element is separated from
unwanted materials.
Smelting
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The substance is melted to
separate it from any remaining
unwanted materials.
Useful Elements in Minerals
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Vein Minerals
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Occur when dissolved metallic
elements travel in fluid form
through weaknesses in rock and
form mineral deposits.
Useful Elements in Minerals
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Titanium
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Found in ilmenite and rutile.
Lightweight and durable
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Used in auto body parts, aircraft,
eyeglasses, etc.