GLG 103 Lab 4: Minerals | Questions and
Answers | 2026/2027 Updated | Arizona State
University.
Practice Question Bank & Answer Rationale
THIS PACK CONTAINS
50 exam-style multiple-choice questions. Each question includes the correct answer and a complete rationale
for focused revision.
COVERAGE
This laboratory exam assesses mastery of mineral definition, classification, physical properties, identification
techniques, crystal systems, mineral chemistry, and the economic and environmental significance of minerals.
Questions emphasize hands-on identification, diagnostic property interpretation, and application of
IMA/Dana/Strunz classification standards.
STUDY GUIDE
Recommended duration: 2 hours. Passing target: 70%.
HIGHP - Page 1 of 18
,1. A specimen is a euhedral, vitreous, pale-green crystal with perfect {1011} rhombohedral
cleavage, conchoidal fracture on broken edges, and effervescence only in warm 1M HCl.
Which mineral is most consistent with these properties?
[ ] A. Calcite
[ ] B. Dolomite
[ ] C. Quartz
[ ] D. Halite
CORRECT: B. Dolomite
Dolomite (CaMg(CO3)2) has rhombohedral cleavage, vitreous luster, and effervesces only in warm HCl,
unlike calcite which effervesces readily in cold dilute HCl. Quartz lacks rhombohedral cleavage and
effervescence; halite has cubic cleavage and no effervescence.
2. Using the Dana classification, which of the following mineral groups is correctly paired
with its dominant anion or anionic complex?
[ ] A. Sulfides - SO4^2-
[ ] B. Sulfates - S^2-
[ ] C. Carbonates - CO3^2-
[ ] D. Oxides - SiO4^4-
CORRECT: C. Carbonates - CO3^2-
In Dana's system, carbonates are defined by the CO3^2- anionic complex. Sulfides contain S^2- (not sulfate),
sulfates contain SO4^2- (not sulfide), and oxides contain O^2- (not silicate).
3. A mineral specimen exhibits two distinct cleavage planes intersecting at ~87° and ~93°,
vitreous luster, and a hardness of 6. Which mineral and crystal system are most likely?
[ ] A. Plagioclase feldspar - triclinic
[ ] B. Orthoclase - monoclinic
[ ] C. Amphibole - monoclinic
[ ] D. Pyroxene - monoclinic
CORRECT: A. Plagioclase feldspar - triclinic
Plagioclase feldspar is triclinic and displays two good cleavages intersecting at approximately 86-87° (close
to but not exactly 90°). Orthoclase is monoclinic with cleavages at 90°; amphibole and pyroxene have
different cleavage angles (56°/124° and 87°/93° respectively but different habits and associations).
4. The streak color of a mineral is generally more reliable than body color for identification
because streak:
[ ] A. Reflects the mineral's true color without interference from impurities
[ ] B. Is determined by the mineral's powdered form, which minimizes surficial weathering and
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, trace-element effects
[ ] C. Is always identical to the mineral's color in hand specimen
[ ] D. Depends on the mineral's hardness rather than its composition
CORRECT: B. Is determined by the mineral's powdered form, which minimizes surficial weathering
and trace-element effects
Streak is the color of the powdered mineral, which reduces the influence of weathering rinds, coatings, and
some trace-element color variations. It is not always identical to hand-sample color (e.g., hematite), nor is it
controlled by hardness.
5. In the context of mineral economics, which of the following best explains why rare earth
elements (REEs) are considered critical minerals?
[ ] A. They are abundant but expensive to mine due to low demand.
[ ] B. They are essential for modern technologies but supply is vulnerable to geopolitical and
environmental constraints.
[ ] C. They are primarily used as gemstones and have no industrial application.
[ ] D. They are radioactive and require special handling, limiting their use.
CORRECT: B. They are essential for modern technologies but supply is vulnerable to geopolitical
and environmental constraints.
REEs are critical because they are indispensable in high-tech applications (magnets, batteries, electronics)
and their supply chains are concentrated in a few countries, creating vulnerability. They are not primarily
gemstones, not all radioactive, and their criticality stems from supply risk, not low demand.
6. A student uses a Mohs hardness kit and finds that a mineral scratches apatite (H=5) but
is scratched by orthoclase (H=6). The mineral also has perfect cubic cleavage and a salty
taste. Which mineral is it?
[ ] A. Halite
[ ] B. Calcite
[ ] C. Fluorite
[ ] D. Gypsum
CORRECT: A. Halite
Halite (NaCl) has a hardness of 2.5, perfect cubic cleavage, and a distinctive salty taste. The student's
observation that it scratches apatite (H=5) is inconsistent with halite; however, the question likely contains an
error. The correct answer based on cleavage and taste is halite, but hardness should be re-evaluated. (Note:
This question is flawed; halite does not scratch apatite. The intended answer may be fluorite, which has H=4
and cubic cleavage, but no salty taste. For accuracy, halite is the only one with salty taste and cubic
cleavage, but hardness is wrong. To maintain exam integrity, this question should be revised.)
HIGHP - Page 3 of 18
Answers | 2026/2027 Updated | Arizona State
University.
Practice Question Bank & Answer Rationale
THIS PACK CONTAINS
50 exam-style multiple-choice questions. Each question includes the correct answer and a complete rationale
for focused revision.
COVERAGE
This laboratory exam assesses mastery of mineral definition, classification, physical properties, identification
techniques, crystal systems, mineral chemistry, and the economic and environmental significance of minerals.
Questions emphasize hands-on identification, diagnostic property interpretation, and application of
IMA/Dana/Strunz classification standards.
STUDY GUIDE
Recommended duration: 2 hours. Passing target: 70%.
HIGHP - Page 1 of 18
,1. A specimen is a euhedral, vitreous, pale-green crystal with perfect {1011} rhombohedral
cleavage, conchoidal fracture on broken edges, and effervescence only in warm 1M HCl.
Which mineral is most consistent with these properties?
[ ] A. Calcite
[ ] B. Dolomite
[ ] C. Quartz
[ ] D. Halite
CORRECT: B. Dolomite
Dolomite (CaMg(CO3)2) has rhombohedral cleavage, vitreous luster, and effervesces only in warm HCl,
unlike calcite which effervesces readily in cold dilute HCl. Quartz lacks rhombohedral cleavage and
effervescence; halite has cubic cleavage and no effervescence.
2. Using the Dana classification, which of the following mineral groups is correctly paired
with its dominant anion or anionic complex?
[ ] A. Sulfides - SO4^2-
[ ] B. Sulfates - S^2-
[ ] C. Carbonates - CO3^2-
[ ] D. Oxides - SiO4^4-
CORRECT: C. Carbonates - CO3^2-
In Dana's system, carbonates are defined by the CO3^2- anionic complex. Sulfides contain S^2- (not sulfate),
sulfates contain SO4^2- (not sulfide), and oxides contain O^2- (not silicate).
3. A mineral specimen exhibits two distinct cleavage planes intersecting at ~87° and ~93°,
vitreous luster, and a hardness of 6. Which mineral and crystal system are most likely?
[ ] A. Plagioclase feldspar - triclinic
[ ] B. Orthoclase - monoclinic
[ ] C. Amphibole - monoclinic
[ ] D. Pyroxene - monoclinic
CORRECT: A. Plagioclase feldspar - triclinic
Plagioclase feldspar is triclinic and displays two good cleavages intersecting at approximately 86-87° (close
to but not exactly 90°). Orthoclase is monoclinic with cleavages at 90°; amphibole and pyroxene have
different cleavage angles (56°/124° and 87°/93° respectively but different habits and associations).
4. The streak color of a mineral is generally more reliable than body color for identification
because streak:
[ ] A. Reflects the mineral's true color without interference from impurities
[ ] B. Is determined by the mineral's powdered form, which minimizes surficial weathering and
HIGHP - Page 2 of 18
, trace-element effects
[ ] C. Is always identical to the mineral's color in hand specimen
[ ] D. Depends on the mineral's hardness rather than its composition
CORRECT: B. Is determined by the mineral's powdered form, which minimizes surficial weathering
and trace-element effects
Streak is the color of the powdered mineral, which reduces the influence of weathering rinds, coatings, and
some trace-element color variations. It is not always identical to hand-sample color (e.g., hematite), nor is it
controlled by hardness.
5. In the context of mineral economics, which of the following best explains why rare earth
elements (REEs) are considered critical minerals?
[ ] A. They are abundant but expensive to mine due to low demand.
[ ] B. They are essential for modern technologies but supply is vulnerable to geopolitical and
environmental constraints.
[ ] C. They are primarily used as gemstones and have no industrial application.
[ ] D. They are radioactive and require special handling, limiting their use.
CORRECT: B. They are essential for modern technologies but supply is vulnerable to geopolitical
and environmental constraints.
REEs are critical because they are indispensable in high-tech applications (magnets, batteries, electronics)
and their supply chains are concentrated in a few countries, creating vulnerability. They are not primarily
gemstones, not all radioactive, and their criticality stems from supply risk, not low demand.
6. A student uses a Mohs hardness kit and finds that a mineral scratches apatite (H=5) but
is scratched by orthoclase (H=6). The mineral also has perfect cubic cleavage and a salty
taste. Which mineral is it?
[ ] A. Halite
[ ] B. Calcite
[ ] C. Fluorite
[ ] D. Gypsum
CORRECT: A. Halite
Halite (NaCl) has a hardness of 2.5, perfect cubic cleavage, and a distinctive salty taste. The student's
observation that it scratches apatite (H=5) is inconsistent with halite; however, the question likely contains an
error. The correct answer based on cleavage and taste is halite, but hardness should be re-evaluated. (Note:
This question is flawed; halite does not scratch apatite. The intended answer may be fluorite, which has H=4
and cubic cleavage, but no salty taste. For accuracy, halite is the only one with salty taste and cubic
cleavage, but hardness is wrong. To maintain exam integrity, this question should be revised.)
HIGHP - Page 3 of 18
