UNIT VIII: MINERALS
After UNIT VIII you should be able to:
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Understand how mineral crystals acquire their shape
Understand the characteristics that define a sample as a mineral
Understand that many minerals are composed of similar elements
Understand the connections between minerals and rocks and that
many rocks contain similar minerals
o Utilize the ESRT to determine human uses of common minerals
o Understand and be able to perform common mineral identification
tests such as:
o Color
o Streak
o Breakage (cleavage or fracture)
o Hardness (Mohs Scale)
o Acid test
o Magnetism test
o Luster
o Density
UNIT VIII vocabulary you should be able to use and understand:
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Element
Atom
Chemical Composition
Mineral
Rock
Organic
Inorganic
Orderly arrangement
Solidification
Lava
Magma
Igneous
Precipitate
Evaporate
Sedimentary
Metamorphic
Crystallize
Crystal
Appearance
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Hardness
Mohs Scale
Luster
Metallic
Non-metallic
Streak
Powdered
Crushed
Breakage
Cleavage
Fracture
Density
Mass
Volume
Acid
Reaction
Magnetic
Abrasive
Lubricant
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Scratch
Impurities
Oxidation
Angular
Physical properties
Chemical properties
5 Fundamental Mineral Characteristics
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Definite chemical composition
Orderly arrangement of atoms
Naturally occurring
Inorganic
Solid
What is a mineral?
 Minerals have a definite chemical
composition unique to that mineral
 The chemical properties a mineral
possesses determines what
humans use that mineral for
 For example, the mineral gibbsite
(Al(OH)3) can be processed to
release the aluminum atoms within
it to be used in manufacturing
Mineral Composition and
Uses
 Use your ESRT page 16
Definite Chemical Composition
 The same elements will make up the same
minerals but impurities/oxidation may at
times change their color
 For example, table salt, or halite, is always
NaCl…composed of a combination of sodium
(Na) and chlorine (Cl) atoms
Other Mineral Uses
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Jewelry
Electronics
Abrasives
Lubricants
A source of metal (ore)/other useful
elements
What are minerals made up of?
 Minerals are composed of 1 or more
elements
 Certain elements contribute color to
minerals (such as these quartz
samples), but color alone is not a
definite way of identifying them
 Many minerals contain the same
elements
 Use your ESRT to identify the
elements
Common Mineral Uses
 Use your ESRT page 16
Orderly Arrangement of Atoms
 Atoms are arranged in an orderly fashion so
that a crystal forms
 This arrangement defines a mineral’s
physical properties such as crystal shape,
hardness, or cleavage
 For example: halite crystals and the atoms
that produce them
Atomic Arrangement and Breakage
 The bonds between atoms (internal atomic
arrangement) in a given mineral determine
how the mineral breaks
 Even, angular breakage is known as cleavage
 Uneven, rough breakage is known as
fracture
 The cleavage of the mineral graphite allows it
to slide off in sheets when pressure is applied,
thus making it ideal as a material in pencil
lead.
Naturally Occurring/Inorganic Solid
 Was not produced by life processes or
humans
 Is not a liquid or a gas
How do minerals form?
 Minerals crystals form due to one of
several rock-forming processes found
in the rock cycle
 Cooling and solidification of
magma/lava
 Precipitating out of a solution,
such as when water evaporates
leaving salt (halite) behind
 Undergoing heat and/or
pressure to form new minerals
Rocks are made up of 1 or more minerals
 This granite has several minerals
within it
Identifying minerals can be difficult,
however many minerals can be identified
with a combination of simple tests.
Pyrite
Mineral Identification: Appearance (color)
 Color and appearance can help identify
some minerals, but it is usually not
enough
Gold
Common Colors
 Use your ESRT page 16
Mineral Identification: Hardness
 Hardness is a measure of how easily a
mineral can be scratched
 In our class “hard” minerals are able
to scratch glass while “soft” minerals
do not
 Talc is a very soft mineral and can be
scratched by a fingernail
 Diamonds are the hardest naturally
occurring material and can only be
scratched by another diamond
Mineral Identification: Mohs Scale
 The Mohs Scale assigns a number to a
mineral’s hardness
 A diamond is a ’10’ since it is the
hardest mineral
 Talc, being one of the softest, is
assigned a ‘1’
 Lower numbers  more easily
scratched
Hardness Values of Common
Minerals
 Use your ESRT page 16
Mineral Identification: Luster
 There are two types of luster we are
concerned with in this course: metallic
and non-metallic
 Metallic luster is when a mineral
appears to be made of metal
 Non-metallic luster can be a variety of
other colors including minerals that
look like glass
Luster of Common Minerals
 Use your ESRT page 16
Mineral Identification: Streak
 The streak of a mineral is the powder
left behind when a mineral is crushed
or is rubbed against an unglazed
porcelain tile
Streak
 Use your ESRT page 16
Mineral Identification: Cleavage and
Fracture
 Cleavage and fracture describe how a
mineral breaks
 Cleavage is a mineral breaking along a
flat plane
 Fracture is uneven and random
breaking
Breakage of Common
Minerals
 Use your ESRT page 16
Mineral Identification: Density
 Determining a mineral’s density
sometimes help determine what it is
 Recall: Density = mass/volume
Mineral Identification: Reaction with
Acid/Magnetic
 Some minerals bubble when acid is
dripped onto them
 Other minerals are magnetic
Other Distinguishing
Characteristics
 Use your ESRT page 16