GLG 103 Lab 8. Metamorphic Rocks |
Questions and Answers | 2026/2027 Updated
| 100% Correct - 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 metamorphic rock classification, formation processes, and
identification. Topics include agents of metamorphism, metamorphic textures, foliated and non-foliated rock
types, protoliths, metamorphic grade, and index minerals. Questions require application of classification
schemes, interpretation of metamorphic environments, and synthesis of mineralogical and textural data.
STUDY GUIDE
Recommended duration: 2 hours. Passing target: 70%.
HIGHP - Page 1 of 18
,1. A geologist collects a rock sample with a strong penetrative foliation defined by aligned
platy minerals, but individual grains are too small to identify with a hand lens. Under the
petrographic microscope, the rock consists of fine-grained white mica and chlorite with a
well-developed slaty cleavage. Which metamorphic rock is most likely, and what is its
protolith?
[ ] A. Phyllite; protolith is shale
[ ] B. Slate; protolith is shale
[ ] C. Schist; protolith is basalt
[ ] D. Gneiss; protolith is granite
CORRECT: B. Slate; protolith is shale
Slate is a fine-grained, foliated metamorphic rock derived from shale, characterized by slaty cleavage and
microscopic mica and chlorite. Phyllite is similar but has a silky sheen and slightly coarser grains; schist has
visible platy minerals; gneiss has compositional banding. The microscopic grain size and dominant
mica/chlorite assemblage confirm slate.
2. Which of the following best explains why quartzite is classified as a non-foliated
metamorphic rock, even when derived from a foliated parent like shale?
[ ] A. Quartzite lacks any preferred mineral orientation because it is composed dominantly of equant
quartz grains that recrystallize without developing foliation.
[ ] B. Quartzite forms only under low-grade conditions where foliation cannot develop.
[ ] C. Quartzite is a product of contact metamorphism, which never produces foliation.
[ ] D. Quartzite is non-foliated because it contains abundant micas that randomize the fabric.
CORRECT: A. Quartzite lacks any preferred mineral orientation because it is composed dominantly
of equant quartz grains that recrystallize without developing foliation.
Quartzite is dominated by equant quartz grains; during recrystallization, quartz does not develop a strong
preferred orientation, so foliation is absent. Low-grade conditions (B) can still produce foliated rocks like slate;
contact metamorphism (C) can produce foliation in some cases; micas (D) would actually promote foliation,
not randomize it.
3. In a regional metamorphic terrane, a sequence of pelitic rocks shows the following
index minerals with increasing distance from a granitic intrusion: chlorite -> biotite ->
garnet -> staurolite -> kyanite -> sillimanite. Which statement correctly interprets this
pattern?
[ ] A. The sequence represents decreasing metamorphic grade away from the intrusion.
[ ] B. The sequence represents increasing metamorphic grade toward the intrusion, with sillimanite
indicating the highest grade.
[ ] C. The presence of kyanite and sillimanite together indicates a low-pressure contact aureole.
[ ] D. The sequence is reversed; chlorite indicates the highest grade.
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, CORRECT: B. The sequence represents increasing metamorphic grade toward the intrusion, with
sillimanite indicating the highest grade.
Index minerals appear in order of increasing metamorphic grade: chlorite (low) to sillimanite (high). The
proximity to the intrusion increases temperature, so grade increases toward the intrusion. Kyanite and
sillimanite together typically indicate medium-pressure regional metamorphism, not a low-pressure contact
aureole. Chlorite is a low-grade mineral.
4. Which of the following metamorphic rocks would most likely form by contact
metamorphism of a limestone protolith?
[ ] A. Marble
[ ] B. Quartzite
[ ] C. Hornfels
[ ] D. Anthracite
CORRECT: A. Marble
Marble forms from the metamorphism of limestone (calcite-rich protolith). Quartzite forms from quartz
sandstone; hornfels forms from any fine-grained protolith (often shale) in contact aureoles; anthracite forms
from coal. While hornfels can form from limestone, marble is the specific product.
5. A metamorphic rock exhibits a banded appearance with alternating light and dark layers
composed of quartz, feldspar, and biotite. The bands are several millimeters thick and the
rock is coarse-grained. Which rock is this, and what is the most likely protolith?
[ ] A. Schist; protolith is shale
[ ] B. Gneiss; protolith is granite or diorite
[ ] C. Phyllite; protolith is slate
[ ] D. Amphibolite; protolith is basalt
CORRECT: B. Gneiss; protolith is granite or diorite
Gneiss is characterized by compositional banding of light (felsic) and dark (mafic) minerals, typically
coarse-grained, and commonly derived from granite or diorite. Schist has a schistose texture (platy minerals)
but not compositional banding; phyllite is fine-grained with a sheen; amphibolite is dominated by amphibole
and plagioclase, not banded.
6. Which of the following statements correctly describes the role of chemically active
fluids in metamorphism?
[ ] A. They inhibit recrystallization by lowering temperature.
[ ] B. They facilitate ion exchange and neomineralization, often introducing or removing elements.
[ ] C. They only cause mechanical deformation without chemical change.
[ ] D. They are only present in contact metamorphism.
HIGHP - Page 3 of 18
Questions and Answers | 2026/2027 Updated
| 100% Correct - 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 metamorphic rock classification, formation processes, and
identification. Topics include agents of metamorphism, metamorphic textures, foliated and non-foliated rock
types, protoliths, metamorphic grade, and index minerals. Questions require application of classification
schemes, interpretation of metamorphic environments, and synthesis of mineralogical and textural data.
STUDY GUIDE
Recommended duration: 2 hours. Passing target: 70%.
HIGHP - Page 1 of 18
,1. A geologist collects a rock sample with a strong penetrative foliation defined by aligned
platy minerals, but individual grains are too small to identify with a hand lens. Under the
petrographic microscope, the rock consists of fine-grained white mica and chlorite with a
well-developed slaty cleavage. Which metamorphic rock is most likely, and what is its
protolith?
[ ] A. Phyllite; protolith is shale
[ ] B. Slate; protolith is shale
[ ] C. Schist; protolith is basalt
[ ] D. Gneiss; protolith is granite
CORRECT: B. Slate; protolith is shale
Slate is a fine-grained, foliated metamorphic rock derived from shale, characterized by slaty cleavage and
microscopic mica and chlorite. Phyllite is similar but has a silky sheen and slightly coarser grains; schist has
visible platy minerals; gneiss has compositional banding. The microscopic grain size and dominant
mica/chlorite assemblage confirm slate.
2. Which of the following best explains why quartzite is classified as a non-foliated
metamorphic rock, even when derived from a foliated parent like shale?
[ ] A. Quartzite lacks any preferred mineral orientation because it is composed dominantly of equant
quartz grains that recrystallize without developing foliation.
[ ] B. Quartzite forms only under low-grade conditions where foliation cannot develop.
[ ] C. Quartzite is a product of contact metamorphism, which never produces foliation.
[ ] D. Quartzite is non-foliated because it contains abundant micas that randomize the fabric.
CORRECT: A. Quartzite lacks any preferred mineral orientation because it is composed dominantly
of equant quartz grains that recrystallize without developing foliation.
Quartzite is dominated by equant quartz grains; during recrystallization, quartz does not develop a strong
preferred orientation, so foliation is absent. Low-grade conditions (B) can still produce foliated rocks like slate;
contact metamorphism (C) can produce foliation in some cases; micas (D) would actually promote foliation,
not randomize it.
3. In a regional metamorphic terrane, a sequence of pelitic rocks shows the following
index minerals with increasing distance from a granitic intrusion: chlorite -> biotite ->
garnet -> staurolite -> kyanite -> sillimanite. Which statement correctly interprets this
pattern?
[ ] A. The sequence represents decreasing metamorphic grade away from the intrusion.
[ ] B. The sequence represents increasing metamorphic grade toward the intrusion, with sillimanite
indicating the highest grade.
[ ] C. The presence of kyanite and sillimanite together indicates a low-pressure contact aureole.
[ ] D. The sequence is reversed; chlorite indicates the highest grade.
HIGHP - Page 2 of 18
, CORRECT: B. The sequence represents increasing metamorphic grade toward the intrusion, with
sillimanite indicating the highest grade.
Index minerals appear in order of increasing metamorphic grade: chlorite (low) to sillimanite (high). The
proximity to the intrusion increases temperature, so grade increases toward the intrusion. Kyanite and
sillimanite together typically indicate medium-pressure regional metamorphism, not a low-pressure contact
aureole. Chlorite is a low-grade mineral.
4. Which of the following metamorphic rocks would most likely form by contact
metamorphism of a limestone protolith?
[ ] A. Marble
[ ] B. Quartzite
[ ] C. Hornfels
[ ] D. Anthracite
CORRECT: A. Marble
Marble forms from the metamorphism of limestone (calcite-rich protolith). Quartzite forms from quartz
sandstone; hornfels forms from any fine-grained protolith (often shale) in contact aureoles; anthracite forms
from coal. While hornfels can form from limestone, marble is the specific product.
5. A metamorphic rock exhibits a banded appearance with alternating light and dark layers
composed of quartz, feldspar, and biotite. The bands are several millimeters thick and the
rock is coarse-grained. Which rock is this, and what is the most likely protolith?
[ ] A. Schist; protolith is shale
[ ] B. Gneiss; protolith is granite or diorite
[ ] C. Phyllite; protolith is slate
[ ] D. Amphibolite; protolith is basalt
CORRECT: B. Gneiss; protolith is granite or diorite
Gneiss is characterized by compositional banding of light (felsic) and dark (mafic) minerals, typically
coarse-grained, and commonly derived from granite or diorite. Schist has a schistose texture (platy minerals)
but not compositional banding; phyllite is fine-grained with a sheen; amphibolite is dominated by amphibole
and plagioclase, not banded.
6. Which of the following statements correctly describes the role of chemically active
fluids in metamorphism?
[ ] A. They inhibit recrystallization by lowering temperature.
[ ] B. They facilitate ion exchange and neomineralization, often introducing or removing elements.
[ ] C. They only cause mechanical deformation without chemical change.
[ ] D. They are only present in contact metamorphism.
HIGHP - Page 3 of 18
