GEO1115_2021_Activity7.4S
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University of Ottawa *
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1115
Subject
Geology
Date
Dec 6, 2023
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docx
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THEME 7 – MINERALS [ 59.25/60 : A+ ]
A
CTIVITY
7.4S – V
ISUAL
IDENTIFICATION
AND
ASSOCIATED
QUESTIONS
( /60)
Reference material:
-
Lecture of associated theme (Brightspace)
-
Glossary (
https://mysite.science.uottawa.ca/dumas/
)
-
Reference document “Section of the lab manual” in Brightspace
Activity:
Answer the questions associated to each of the following pictures. N.B. The same mineral can come back
more than once. Only the minerals highlighted in yellow in the reference material (Section of Lab Manual) are subject to study here.
Mineral 1 ( /5)
a)
Does this mineral have a metallic or a non-metallic luster?
-
Non-metallic
b)
Give a more precise qualifier for the luster of this mineral.
-
vitreous
c)
Based on the picture, what is the hardness of this mineral? Justify your answer.
-
Greater than 5.5 because it is able to scratch the glass
d)
Knowing that this mineral has no cleavage, what mineral is it?
-
Quartz
e)
Give the chemical formula of this mineral.
-
SiO
2
Mineral 2 ( /6)
a)
Is the cleavage shown in the picture at 90° or not?
-
Yes
b)
Knowing that this mineral is scratched by the penny but not by the fingernail, what mineral is it?
-
Halite
c)
Referring to the Identification Tables, describe the cleavage of this mineral (number of directions and angles), and give the name given to this type of cleavage.
-
Cubic, 3 directions at 90
°
d)
Although not diagnostic, what is the streak of this mineral?
-
White
e)
Give another diagnostic property of this mineral which is very easy to test without any tools other than the senses of the body.
-
It tastes salty
f)
What is the chemical formula of this mineral?
-
NaCl
Mineral 3 ( /5)
a)
What physical property is shown in the picture above?
-
Effervescence to acid
b)
Knowing that the reaction is strong and instantaneous, what mineral is it?
-
Calcite
c)
Describe the cleavage of this mineral (number of directions and angles).
Rhombohedral, 75
°
-105
°
d)
Give another diagnostic physical property of this mineral.
-
Hardness of 3 therefore softer than glass
e)
If the reaction to HCl was present, but not as strong, what mineral could it be?
-
Dolomite
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Mineral 4 ( /5)
a)
If this mineral has a basal cleavage, what mineral is it?
-
Biotite
b)
Give the hardness of this mineral. How could you confirm this (summarize the tests to be performed)?
-
The hardness is 2-3. You can test this by seeing if it can scratch glass(5.5) and if it can be scratched by a penny(3.5) and a fingernail(2.5).
c)
To which group of silicates does this mineral belong (what is the structure of silicates)?
-
It is a sheet silicate of Fe-Mg
d)
What other mineral belongs to the same group of minerals and is very similar to this one?
-
Muscovite
e)
What is the major difference between these two minerals (how could you easily tell them apart)?
-
Colour, muscovite is a light colour and biotite is dark.
Mineral 5 ( /5)
a)
Does this mineral have a metallic or a non-metallic luster?
-
Non-metallic
b)
Knowing that it does not scratch glass and does not produce effervescence, what three minerals could it be?
-
Muscovite, Talc, or Gypsum
c)
Explain how you would go about determining which of the three minerals named above it is, highlighting the diagnostic properties of these minerals.
-
Talc has a greasy feel and Gypsum has 1 perfect and 2 good cleavage planes
d)
If this mineral produces very small, flat flakes when scratched, what mineral is it?
-
Talc
e)
What diagnostic property of this mineral is responsible for the formation of these small flakes when scratched? In other words, what property causes it to break like this? Explain.
-
The cleavage forms folia
Mineral 6 ( /4)
a)
Is this mineral translucent or opaque?
-
translucent
b)
Knowing that this mineral has no cleavage and it scratches glass, what mineral is it?
-
quartz
c)
What is the name given to the way this mineral breaks?
-
Conchoidal fractures
d)
Give one use of this mineral.
-
caulking
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Mineral 7 ( /4)
a)
Does the above mineral have a metallic or a non-metallic luster?
-
metallic
b)
Describe the color of this mineral.
-
Pale greenish yellow, gold
c)
If the streak for this mineral is very dark (greenish black to black), what mineral is it?
-
Pyrite
d)
What is the chemical formula of this mineral?
-
FeS
2
Mineral 8 ( /5)
a)
Based on this picture, what is the hardness of this mineral? Justify your answer.
-
Greater than 5.5 as it was able to scratch the glass(hardness of 5.5) and was not scratched by the
penny(hardness of 3.5)
b)
What is the name given to the parallel and very fine striations on the surface of this mineral (enlarge the area circled in red)?
-
Polysynthetic twinning
c)
Based on these two properties, give the name of this mineral.
-
Plagioclase Feldspar
d)
Although it can not be easily seen in this picture, describe the cleavage of this mineral (number of directions and angles) based on the Identification Tables, and give the name given to this type of cleavage.
-
Prismatic with intersections between two cleavage planes at 90
°
e)
What other mineral belongs to the same group of minerals and is very similar to the one shown in the picture?
-
Potassium Feldspar
Mineral 9 ( /5)
a)
Are the cleavage planes shown in this picture at 90° to each other, or not (enlarge the picture if necessary)? If not, what is the approximate cleavage angle?
-
No, approximately 75
°-105°
b)
Knowing that there are three directions of cleavage at these same angles, what is the name given to this type of cleavage?
-
Rhombohedral
c)
Knowing that this mineral is not scratched by the penny, but is scratched by the steel nail, what mineral is it?
-
Dolomite
d)
Would you expect this mineral to produce effervescence with HCl? Explain.
-
Dolomite produces effervescence with HCl only when powdered.
e)
Name another mineral that is very similar to this one and with which it can easily be confused.
-
Calcite
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Mineral 10 ( /6)
a)
Is this mineral translucent or opaque?
-
Translucent
b)
What physical property of this mineral explains why it breaks into thin sheets, as shown in the picture?
-
It has basal cleavage
c)
To which group of silicates does this mineral belong (what is the structure of silicates)?
-
Sheet silicate of K-Al
d)
Knowing that this mineral is scratched by the fingernail, but with a little difficulty, what is its approximate hardness?
-
Approximately 2-2.5
e)
Name this mineral.
-
Muscovite
f)
What other mineral belongs to the same group of minerals and is very similar to the one in the picture, but darker?
-
Biotite
Mineral 11 ( /5)
a)
Describe the color of the main mineral forming this rock.
-
Red with patches of dark gray
b)
If this sample is weakly magnetic, what mineral is it?
-
Hematite
c)
Give one use of this mineral.
-
Used in red pigment
d)
What other mineral is magnetic?
-
Magnetite
e)
Compare the streak of these two minerals.
-
The streak of hematite is red-brown, whereas the streak of magnetite is black
Mineral 12 ( /5)
a)
Is this mineral opaque or translucent?
-
translucent
b)
Knowing that this mineral is scratched by the fingernail and does not taste salty, what two minerals could it be?
-
Gypsum or Talc
c)
Which of these two minerals would be easier to scratch with your fingernail? Briefly justify your answer.
-
Talc has a lower hardness(1) compared to Gypsum(2) therefore talc would be easier to scratch
d)
If this mineral does not have a greasy or waxy feel, what mineral is it?
-
Gypsum
e)
Give one use of this mineral.
-
Used in plaster, such as drywall or casts
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