Mineral Mystery Lab - Student Handout
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Colorado State University, Fort Collins *
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Course
121
Subject
Geology
Date
Dec 6, 2023
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GEOL 121 Tim Trosel
Lab Section: L18
MINERAL MYSTERY LAB
Learning Objectives
At the end of this lab students will be able to:
●
Observe characteristics of minerals. ●
Describe differences in physical properties of minerals
●
Use physical properties to identify minerals.
●
Develop and produce a system for identifying different minerals via a flow chart.
Introduction
Ultimately, geology is about storytelling; we can think of the entire Earth’s history as a book, the pages in the book are filled with stories that we developed by looking at the rocks that form our planet. Minerals that make up those rocks help us identify the rocks, so we can tell their stories.
We also use minerals in our lives every day, often without even noticing. Minerals are in your cell phone, your car, your countertops (well, some of our countertops anyway) and even your walls. So, not only do minerals help us tell Earth’s story but they also help make our modern lives possible. Minerals come in all shapes, colors, and sizes but they share common characteristics that we can use to sort them into groups. In this lab, you take on the role of a mineralogist by testing various physical properties, sorting minerals into categories with similar characteristics, and then creating a flowchart to use to identify minerals.
1
Mineral Mystery Lab GEOL 121
Step 1: Search for clues
Observe the grid of minerals in front of you. None of them are currently named - that’s okay! Before we get into labeling, let’s take a close look at each of the minerals.
Q1
. What are some physical characteristics that multiple minerals share? What are three different ways that you could divide these minerals into 2–3 groups based on those characteristics? Option 1
Group 1 characteristic:
Light color
Group 2 characteristic:
Dark color
Group 3 characteristic (optional):
Mineral(s): A B C F G K
Mineral(s): D E H I J L
Mineral(s):
Option 2
Group 1 characteristic:
Dull
Group 2 characteristic:
Shiny
Group 3 characteristic (optional): Translucent
Mineral(s): A D G H K L
Mineral(s): E I J
Mineral(s): B C F
Option 3
Group 1 characteristic:
Smooth
Group 2 characteristic:
Rough
Group 3 characteristic (optional):
Mineral(s): A B C G J K
Mineral(s): D E F H I L
Mineral(s):
Once you have come up with three different ways to divide these minerals into groups based on
their physical characteristics, compare the groups you made with the other pair of students in your small group. What groups are the same? What groups are different? Is there more than one valid way to group the minerals?
2
Mineral Mystery Lab GEOL 121
Q2
. Take a look at the tools next to your mineral grid. Try out some of these tools on your minerals. Some tools are for getting a closer look at the minerals, some are for scratching the minerals, and some are for checking the streak a mineral makes. The HCl bottle is used
to check for effervescence (i.e. a fizz reaction). Are there any similarities between how different minerals interact with particular tools? What are some other ways that you could divide these minerals into 2–3 groups, based on those similarities?
Option 1
Group 1 characteristic:
Streak on plate
Group 2 characteristic:
No streak on plate
Group 3 characteristic (optional):
Mineral(s): A C D E G H I K L
Mineral(s): B F J
Mineral(s):
Option 2
Group 1 characteristic:
Magnetic
Group 2 characteristic:
Non-Magnetic
Group 3 characteristic (optional):
Mineral(s): D
Mineral(s): A B C E F G H I J K L
Mineral(s):
Option 3
Group 1 characteristic:
Reacts to acid
Group 2 characteristic:
No reaction to acid
Group 3 characteristic (optional):
Mineral(s): G
Mineral(s): A B C D E F H I J K L
Mineral(s):
3
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Mineral Mystery Lab GEOL 121
Q3
. Compare the following pairs of minerals and list any differences that you notice between the
two. Differences in terms of physical characteristics and differences in terms of interaction with tools are both valid!
Mineral A
Mineral F
●
More opaque
●
Slightly better cleavage
●
White streak
●
~4.5 Hardness
●
Translucent
●
Poor cleavage
●
No streak
●
7 hardness
Mineral B
Mineral J
●
Lighter color
●
More translucent
●
Slightly more perfect cleavage
●
2 hardness
●
Dark color
●
Not as translucent
●
Not as perfect cleavage, leaves
●
2.5 hardness
Mineral C
Mineral G
●
No reaction to acid
●
Translucent
●
3 hardness
●
Thick streak
●
Reacts to acid
●
Opaque
●
4.5 hardness
●
Thin streak
Mineral D
Mineral H
●
4.5 hardness
●
Less luster
●
Magnetic
●
6 hardness
●
Higher luster
●
Non-Magnetic
Mineral E
Mineral I
●
Gold color
●
6 hardness
●
More luster
●
Silver color
●
2.5 hardness
●
Slightly less luster
4
Mineral Mystery Lab GEOL 121
Mineral H
Mineral L
●
All black
●
More luster
●
Slightly better cleavage
●
Greenish Black
●
Dull luster
●
Poor cleavage
Again, reconvene with your small group. For each mineral pair, discuss what difference you think will be the most useful
for distinguishing between the two minerals. Come to a consensus for each mineral pair within your small group. Circle or highlight that difference in each of the tables above.
Q4
. Now put together all of your observations! List 3–5 physical properties for each mineral: Mineral A
●
Hardness 4.5
●
2 90 degree plane cleavage
●
White and brown color
●
White streak
Mineral B
●
Hardness 2
●
Translucent
●
Perfect cleavage
●
No streak
Mineral C
●
Hardness 3 ●
Colorless or translucent
●
Perfect 3 points at 90, cleavage
5
Mineral Mystery Lab GEOL 121
Mineral D
●
Magnetic
●
Very little luster
●
No cleavage
●
Hardness 6
Mineral E
●
High luster
●
Hardness 6
●
Brass Color
●
No Cleavage
Mineral F
●
Translucent
●
Hardness 7
●
White color
●
No streak
Mineral G
●
White color
●
White streak
●
Hardness 3 ●
Perfect 3 plane cleavage 75 degrees
Mineral H
●
Black color
●
Slight luster
●
2 direction cleavage
●
White streak
Mineral I
●
Silver color
●
High luster
●
Very dense
●
Hardness 2.5
Mineral J
●
Perfect cleavage
●
Black color
●
High luster
●
Hardness 2.5 - 3
Mineral K
●
Orange color
●
White streak
●
Perfect cleavage
●
Hardness 6
Mineral L
●
Hardness 6
●
2 imperfect cleavage
●
Black/Green Color
●
No luster
Step 2: Identify the suspects Q1
. What did you learn from Step 1?
I learned all the physical properties of the provided minerals.
Q2
. Applying your understanding of mineral physical properties, use the following table (which contains the name and physical properties of minerals) to construct a Mineral Identification Flow Chart. Follow the flow chart, answering the questions for each mineral. Place the correct mineral names in the boxes.
Quartz F
SiO
2
Color: colorless, white, pink, any color
Streak: white/colorless
Luster: glassy
Hardness: 7
Plagioclase Feldspar A
NaAlSi
3
O
8
to CaAl
2
Si
2
O
8
in varying proportions
Color: white to green-gray
Streak: white/colorless
Luster: milky to translucent
Hardness: 6
Cleavage: good, 2 planes at 90º
Amphibole L
Ca
2
(Mg,Fe(Ca,Na)
2-
3
(Mg,Fe
+2
,Fe
+3
,Al)
5
Si
6
(Si,Al)
2
O
22
(OH)
2
Color: black
, dark green, dark brown, dark gray
Streak: white/colorless
Luster: vitreous to dull
6
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Mineral Mystery Lab GEOL 121
Conchoidal fracture common
Specific Gravity: 2.65
Striations on cleavage planes
Specific Gravity: 2.62–2.75
Hardness: 6
Cleavage: Imperfect 2 directions at 56° and 124° / uneven
Specific Gravity: 3–3.4
Halite C
NaCl
Color: colorless
Streak: white/colorless Luster: glassy
Hardness: 2.5
Cleavage: perfect, 3 planes @
90º
Salty taste
Muscovite (mica) B
KAl
2
(AlSi
3
O
10
)(F,OH)
2
Color
: colorless to pale yellow/gold
Streak: white/colorless
Luster: glassy, milky
Hardness: 2–2.5
Specific Gravity: 2.8–2.9
Cleavage: perfect in 1 direction; Thin, elastic sheets of micas
Galena I
PbS
Color: gray
Streak: gray
Hardness: 2.5
Cleavage: good, 3 planes @ 90º
Specific Gravity: 7.5 (very dense)
Sulfur smell on fresh surfaces
Pyrite (fool’s gold) E
FeS
2
Color: brassy yellow
Streak: green-black to black
Luster: metallic
Hardness: 6–6.5
Specific Gravity: 5.02
Magnetite D
Fe
3
O
4
Color: dark gray to black
Streak: black
Luster: metallic
Hardness: 5.5-6.5 Specific Gravity: 5.2
Cleavage: none
Magnetic
Biotite J
K(Mg,Fe)
3
AlSi
3
O
10
(OH)
2
Color: brown to black
Streak: white to gray
Luster: pearly to submetallic
Hardness: 2.5-3
Specific Gravity: 2.7-3.4
Cleavage: Single perfect cleavage to produce thin flexible sheets or flakes.
Calcite G
CaCO
3
Color: colorless, white, yellow
Streak: white/colorless
Luster: glassy
Hardness: 3
Specific Gravity: 2.71
Cleavage: perfect, 3 planes @
75º
Effervesces in dilute HCl acid
Pyroxene H
(NaCa)(Mg,Fe,Al)(Al,Si)
2
O
6
Color: Usually dark green
, dark brown or black
Streak: white, greenish white or gray
Luster: vitreous (glass-like)
Hardness: 5-6
Specific Gravity: 3.2-3.5
Cleavage: Two directions, that meet at nearly right angles (87°
and 93°)
Potassium Feldspar K
KAlSi
3
O
8
Color: typically shades of peach, orange, or red
Streak: white
Luster: crystals are vitreous (glass-like) to porcelaneous (porcelain-like)
Hardness: 6
Specific Gravity: 2.6
Cleavage: One perfect cleavage and one good cleavage, meet at nearly 90°
Step 3: Solve the Mystery!
7
Mineral Mystery Lab GEOL 121
Q1. Applying your understanding of mineral physical properties, use flow chart you made in the previous step to identify your 12 unknown mineral specimens. We will identify Mineral A and Mineral B together as a class. Work in pairs and then share your findings with your larger group. Place your answers in the space provided, in the table below.
Enter the names of the minerals in the spaces below.
Mineral A = Plagioclase Feldspar
Mineral E = Pyrite
Mineral I = Galena
Mineral B = Muscovite
Mineral F = Quartz
Mineral J = Biotite
Mineral C = Halite
Mineral G = Calcite
Mineral K = Potassium Feldspar
Mineral D = Magnetite
Mineral H = Pyroxene
Mineral L = Amphibole
Step 4: Reflection
Q1
: What did you enjoy about this lab?
8
Mineral Mystery Lab GEOL 121
I thoroughly enjoyed using the different tools to learn the different physical properties of each mineral.
Q2
: What was difficult about this lab?
It was difficult to distinguish the minerals from one another when they share many physical properties.
Q3
: What questions do you still have about identifying minerals?
How were the names chosen for each mineral besides magnetite?
9
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