Lab 4 -Identification of Minerals-In class lab
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CUNY College of Staten Island *
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Course
101
Subject
Geology
Date
Dec 6, 2023
Type
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6
Uploaded by ProfessorMetalEchidna20
1
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Lab 4 Minerals
In Class Lab
Read Chapter 3 of “Earth Science” and review your lecture notes on minerals.
In order to identify minerals, geologists describe a selection of physical properties that,
when used together, define each of the common minerals.
Color
: This is the color you see when you look at the mineral. Be specific i.e. say “red,
brown and yellow” rather than “multicolored” or “various”. Also distinguish between white
and clear. This may be different to another sample of the same mineral.
Streak
: This is the color of the mineral when it is powdered. To test for this color, you
draw the mineral across the surface of a piece of white porcelain, called a
streak plate
. The
mark the mineral leaves on the surface shows the color of its streak. This color is much less
variable than the general color you see when looking at the whole mineral. If a mineral is
harder than the streak plate, it will not powder. Be careful to differentiate between a
mineral with no streak (because it’s too hard) and one with a white streak.
Luster
: This is a property of the mineral’s surface, and is independent from its color. It
describes how the mineral surface reflects light. Two sample of the same mineral may have
a different luster.
Metallic – mineral appears shiny like a new coin
Vitreous – mineral looks glassy
Resinous – mineral surface looks like resin or plastic
Pearly – mineral surface looks like a pearl or the inside of a seashell
Dull – mineral reflects little light and looks like dirt or soil
Greasy – mineral surface has a greasy look and feel
Jessicatlart
1012
2
Hardness
: This is a measure of how resistant a
mineral is to abrasion, and is measured on a
scale called Mohs scale. The hardest mineral is
diamond, with a hardness of 10, and the softest is
talc, with a hardness of 1. Harness is measured by
testing whether a mineral may be scratched by
another mineral of known hardness (see table on
right), or by another object of known hardness. In
the lab you will be testing minerals with your
fingernail (hardness 2.5), a copper penny (hardness
3.5) and a glass plate (hardness 5.5). You will
therefore be able to define hardness as < 2.5, 2.5 –
3.5, 3.5 – 5.5 or > 5.5.
Cleavage and fracture
: There are two different ways that a mineral may break. If it breaks
along an irregular surface, the mineral is described as having
fracture
. However, if it
breaks along a flat surface, parallel to one of the faces of the crystal, then it is described as
having
cleavage
. Such cleavage planes are related to the chemical structure of the crystal.
The angles between cleavage planes are often unique to a particular type of mineral,
making them a good guide to identification.
E"ervescence
: A mineral may react (/zz) when a drop of weak hydrochloric
acid is placed on its surface.
Habit
: Characteristic form in which the mineral grows. Related to crystal
structure.
Mineral
Hardness
Talc
1
Gypsum
2
Calcite
3
Fluorite
4
Apatite
5
Orthoclase
6
Quartz
7
Topaz
8
Corundum
9
Diamond
10
4
In-class
lab
E
xercises
The mineral set is in the top drawer of the bench
Required materials
Pencil
Magnifier
Glass plate
Streak plate
Penny
Mineral set
Acid
Part
1
–
Hardness
Take the following minerals from the box:
1.
Graphite
5.
Hematite
7.
Quartz (crystal)
13.
Calcite
1.
Using your fingernail, the penny and the glass plate, list these minerals in order of their
hardness.
Softest
Hardest
2.
Describe in your own words how you made this determination.
-
-
-
Graphite
Hematite
calcite
Quartz
we
scratched
all
the
minerals
on
the
hard
plate
and
saw
which
minerals
stedsediments.
The
one
that
shed
the
most
is
the
softest.
The
one
that
did
not
shed
is
the
hardest.
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5
Part
2
–
Cleavage
and
Fracture
Take the following minerals from the box:
8.
Quartz (milky)
11.
Halite
13.
Calcite
14.
Gypsum
3.
Sketch the shape of each sample, and show any cleavage planes that you can identify.
4.
Which sample has fracture, but no cleavage planes?
5.
All of the other samples have the same number of cleavage planes – how many cleavage
planes to they have?
d)
3
cleavage
(4)
E
2
cleavages
i)
13
cleavage
13)
]
cleavaces
rock
9,
3,
4,
10
3
planes
of
cleavage
6
6.
In which sample are the cleavage planes at right angles?
7.
The other 2 samples have very similar cleavage plane angles, but one effervesces when
a drop of acid is placed on its surface. Which sample does this?
8.
Describe in your own words how you would identify each of these samples if you were
given a group of unknown minerals that all had this similar clear/white color.
Part
3
–
Color,
streak
and
luster
Take the following minerals from the box:
2.
Galena
4.
Pyrite
5.
Hematite
15.
Microcline Feldspar
9.
What is the color, streak and luster of each of the minerals?
2.
4.
5.
15.
90
Angle
(ii)
(13)
not
at
900
Angle
sample
13
you
would
do
a
scratch
test
to
see
if
any
sediments
shed
of
the
mineral
Black
Black
Red
↑
Nene
7
Take sample #15, and check its hardness using the glass plate. What does this tell you about
the streak of this sample?
10. In which samples are the color and streak the same?
11. In which samples are the color and streak different?
12. Take a look at other samples of hematite from other sample boxes around the room. Do
they all have the same color, luster and streak? Describe the variability.
13. What is the one thing that is consistent among all of the hematite samples?
Sample
15
did
scratch
the
glass
so
this
tells
you
the
mineral
is
harder
then
the
glass.
sample
1,
2,16
sample
3,
10,
18,5
They
would
all
have
the
same
streak
color
(brown
color)
they
would
also
↑
all
be
matalic.
Yes
Streak
color
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