PG_7103_L03_Minerals
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Pace University *
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101
Subject
Geology
Date
Apr 3, 2024
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docx
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PRE-LAB QUESTIONS
1.
Which of the following terms are useful for describing the luster of nonmetallic minerals? (Select all that apply.)
a.
Vitreous
b.
Translucent
c.
Earthy
d.
Shiny
e.
Silky
2.
True or False? A mineral with a lower Mohs Hardness number will scratch a mineral with
a higher Mohs Hardness number.
3.
___ refers to the way the surface of a mineral reflects light.
4.
Describe why it is not a good idea to use only color and clarity to identify a mineral.
©2016, eScience Labs
Minerals
EXERCISE 1 DATA SHEET
Table 3. Specific Gravity
Mineral
Letter
Dry Mass (g)
Total Volume
(mL)
Displaced Volume
(mL)
Specific Gravity
A
30.4
110
10
3.04
B
41.6
109
9
4.62
D
32.4
112
12
2.68
E
1.2
101
1
1.20
F
27.5
111
11
2.50
G
28.3
112
12
2.36
H
3.6
102
2
1.80
I
25.4
108
8
3.18
©2016, eScience Labs
Minerals
EXERCISE 1 POST-LAB QUESTIONS
1.
Which
mineral had the highest specific gravity? What does this tell you about the elements (or compounds) that make up this mineral? (Hint: Think about how elements are arranged on the periodic table based on their properties.)
Mineral B had the highest specific gravity. Based on this information, it tells us that the higher the specific gravity, the “heftier” and denser the mineral is.
2.
Why is it helpful to measure the specific gravity of a mineral?
It is helpful to measure the specific gravity of a mineral because it provides a quantitative
measure of its density compared to the density of water. As there is only a certain number of minerals that have that specific gravity, knowing the specific gravity of a mineral can help you narrow down the possible identity of the unknown mineral.
3.
How would a mineral’s specific gravity be affected if the mineral contained impurities (other elements not normally part of a mineral’s atomic structure)?
If the mineral contained impurities, its specific gravity would be affected and result in a higher or lower specific gravity.
©2016, eScience Labs
Minerals
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EXERCISE 2 DATA SHEET
Table 5. Mineral Identification
Mineral
Sample
Color/
Clarity
Luster
Streak
Hardness
Cleavage
Other
Distinctive
Properties
Mineral Name
A
white
vitreous,
glassy
no streak
7
conchoidal
fracture
scratches
glass;
prismatic
quartz
B
brassy
yellow/gold
metallic
grayish
black
6-6.5
uneven
fracture
heavy; cubic,
octahedral
pyrite
D
white
vitreous,
silky
white
2
one
(perfect)
tabular,
prismatic;
fluorescent
under UV light
gypsum
E
clear
metallic
brown
vitreous
white
2-2.5
one
(perfect)
easily splits
into thin
sheets; tabular
muscovite
F
pink with
streaks of
red and
black
vitreous
white
6
two at 90
degrees
prismatic
potassium
feldspar
G
white
vitreous
white
2.5
three at 90
degrees
cubic
halite
H
black
vitreous
gray-black
2.5-3
one
(perfect)
easily splits
into thin
sheets
biotite
I
clear blue
vitreous
white
4
octahedral
cubes,
octahedral;
fluorescent
under UV light
fluorite
EXERCISE 2 POST-LAB QUESTIONS
1.
What properties of Mineral B could be used to distinguish it from gold? Write
the name of
Mineral B, its common nickname (see Figure 3) and fill in the data about each of the properties. Compare the differences between the two minerals and summarize your findings in a short paragraph. Is the nickname accurate? Why or why not?
©2016, eScience Labs
Minerals
Properties of Mineral B:
●
Name: pyrite
●
Nickname: Fools gold
●
Color/Clarity: brassy yellow/gold
●
Luster: metallic
●
Streak: grayish black
●
Hardness: 6
●
Cleavage: uneven fracture
●
Specific Gravity: 4.65
Despite the similar metallic lusters between the two minerals, there are many differences between pyrite (Fools Gold) and gold. When comparing the streak of the two minerals, gold has a yellow streak, which highly differentiates itself from the grayish black streak of pyrite. Native gold also has a lower streak level of 2.5-3, differing greatly from pyrite’s hardness of 6. Additionally, native gold has a high specific gravity with an absent cleavage due to its ductility and malleability, in comparison to pyrite’s low specific gravity and uneven fracture. Although ©2016, eScience Labs
Minerals
their properties may be different, pyrite does live up to its nickname when it comes to the general appearance of luster between pyrite and native gold.
2.
Marble is a rock that is composed primarily of the carbonate minerals calcite (CaCO
3
) and dolomite (Ca,Mg(CO
3
)
2
). In this exercise, you saw the way carbonate minerals react to a drop of acetic acid. Based on this observation, why do you think people who care for
monuments and sculptures made of marble are concerned about acid rain? People who care for monuments and sculptures made of marble are concerned about acid rain because when it interacts with carbonate minerals in marble, it leads to the figure’s degradation and dissolution. As marble is composed of calcite and dolomite, two
minerals that react to acid, it can cause the surface of the marble to dissolve or erode over time. Over time, this process can lead to the formation of pits and grooves on the surface of the marble as it disintegrates, raising the concern for the structural integrity and physical appearance of the figure. ©2016, eScience Labs
Minerals
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