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3-1 What is a mineral?
3-2 Identifying minerals?
(epsomite)
{enrich}
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What is a Mineral?
More than 4,000 minerals (40-50 new minerals
identified each year!)
but only 100 common minerals
about 20 minerals make up most of Earth’s crust
native elements occur in nature in pure form (ex:
gold, copper, diamond, sulfur, graphite, silver, and
platinum)
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Most minerals are COMPOUNDS… (a
chemical combination of two or more
elements), while rocks are mixtures of
minerals (and sometimes organic matter
like shells)
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Some minerals are elements (like copper, gold
and diamonds)
{enrich}
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Classification of minerals
95% of the earth’s
crust is made of
silicates (minerals
made of silicon and
oxygen): ex: quartz
SiO2)
sulfide (+ sulfur) ex:
cinnabar (HgS)
sulfate (+sulfur & O)
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carbonate (C & O) ex:
calcite: CaCO3
oxide (+oxygen) ex:
corundum: Al2O3
halide –ex: salt
Characteristics of ALL minerals: (INSCC)
--foldable-
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Inorganic
Natural
Solid
Compound (or
element)
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Crystal system
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Inorganic
– never alive
– not from
something alive
– rocks can have
organic matter
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Naturally occurring
– not synthetic or
artificial or manmade
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Solid
– at room temperature
Chemical composition
– some single element
in pure form (native
elements) like copper,
diamond, sulfur
– most are compounds
like quartz (SiO2) and
cinnabar (HgS)
– rocks are mixtures
– Can you read a
chemical equation?
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Crystal system
– repeating pattern
with flat sides
(called faces)
– most are only
visible with a
microscope
8 ways to test the identify of a mineral
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1--hardness
2--color
3--streak color
4--luster
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5--density
6--crystal structure
7--cleavage/fracture
8--special properties
Hardness
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how easy is it to scratch the mineral?
Moh’s scale
– 1812 by Friedrich Mohs
– 1 (talc) - 10 scale (diamond)
– common substances:
 fingernail=2.5
 penny=3-3.5
 glass=5.5-6
 steel=5-5.5
 streak plate=
6.5-7.5
Colors of QUARTZ
Two colors
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Color
– easy but not reliable
– color may change
over time
– some minerals have
MANY colors (like
quartz)--due to
impurities
– many minerals have
the same color
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Streak Color--practice
– more reliable than
regular color
– color of its powder
– use streak plate
(unglazed tile)
– examples:
 pyrite=black
 gold=golden, yellow
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Luster
– how a mineral
reflects light from
its surface
– 1. metallic (shiny)
– 2. nonmetallic:
glassy, dull,
earthy, waxy,
pearly
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Density
– mass/volume
– remains the same
(no matter the
specimen size)
– also called “heft”
– may use “specific
gravity” (same as
density, but no
units)
Types of luster
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 Cleavage/Fracture (paper towel demo)
Crystal System
– how a mineral BREAKS
– Example: cubic– 1. Cleavage=smooth break
– Example:
hexagonal
– 2. Fracture=irregular break—
rough, jagged, or curved (most
minerals have fracture)
 quartz=curved, shell-like surface
 copper and iron=hacky fracture
(forms jagged points)
Special Properties
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Fluorescence (glow
under UV light)-scheelite
magnetic--magnitite
radioactive--uraninite
fizzes (gives off CO2)
in acid– calcite
(demo)
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Very malleable (easy
to shape)--gold
earthy odor--clay
soapy feeling--talc
feels greasy--graphite
double refraction-optical calcite
Special Properties:
A rock is a mixture of _____________.
 minerals
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Mystery mineral game:
Pick a mineral from pp. 800-801
 other classmates must ask yes/no questions
to determine the identity of the mystery
mineral (like “20 Questions)
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LAB: What mineral do you have?
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Find color and streak color
What is the luster?
Find the hardness (a range)
Find density (use water displacement for
volume)—could use “heft”
AFTER 2-4 tests are completed, try to identify
the mineral, then...
Bring the mineral to Mrs. McMullan when
finished to see if you are correct and to get
another mineral to identify.
Questions for review
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Which of the following definitions best
describes a MINERAL?
– a. a substance that cannot be separated or
broken down into simpler substances by
chemical reactions
– b. a substance made up of atoms of two or
more different elements joined by chemical
bonds
– c. a naturally formed inorganic solid that has a
definite crystalline structure
– d. a solid whose atoms, ions, or molecules are
arranged in a definite pattern
Minerals that contain one or more elements
combined with silicon and oxygen are
called _________ {enrich}
 silicates
 Which mineral can be identified by tasting?
 halite (salt)
 What is the difference between a mineral
and a rock?
 Minerals are elements or compounds.
 Rocks are mixtures (or minerals).
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