ESS 101-B – LABORATORY 3B: MINERAL
IDENTIFICATIONINTRODUCTION TO GEOLOGY
AND SOCIETAL IMPACTS | COMPREHENSIVE
LABORATORY STUDY GUIDE, QUESTIONS &
ANSWERS | 2026/2027 UPDATED EDITION
PART I — Mineral Identification Fundamentals
Question 1
A student is given an unknown mineral and records that it is naturally occurring, solid,
inorganic, crystalline, and has a restricted chemical composition. Which conclusion is best?
A. It satisfies the standard definition of a mineral.
B. It must be a rock because it contains crystals.
C. It must be synthetic because its chemistry is restricted.
D. It cannot be identified without knowing its geologic age.
Correct Answer: A. It satisfies the standard definition of a mineral.
Rationale: A mineral is generally characterized as a naturally occurring, inorganic solid with
an ordered internal structure and a definite chemical composition or limited compositional
range. These criteria distinguish minerals from ordinary manufactured substances and rocks.
Identification then relies on physical and chemical properties rather than age alone.
Question 2
When comparing two unknown specimens, which observation most directly describes how
each specimen interacts with visible light?
A. Streak
B. Luster
C. Hardness
D. Cleavage
Correct Answer: B. Luster
Rationale: Luster describes the way light reflects from a mineral's surface. Common
descriptive categories include metallic, vitreous, pearly, and other nonmetallic appearances.
Streak concerns powdered color, hardness concerns scratch resistance, and cleavage
concerns preferred breakage directions, so none directly describes surface reflection.
,Question 3
A mineral appears metallic and reflective even though its streak is dark gray. Which property
is being described by the word “metallic”?
A. Hardness
B. Streak
C. Luster
D. Cleavage
Correct Answer: C. Luster
Rationale: Metallic is a luster classification describing strong, metal-like reflection from a
mineral surface. Streak describes the powder produced during a streak test, while hardness
and cleavage describe different physical behaviors. Therefore, the observation that the
specimen looks metal-like concerns luster specifically.
Question 4
A student rubs an unknown mineral across an unglazed porcelain plate and observes a fine
white powder. What property has been measured?
A. Fracture
B. Cleavage
C. Hardness
D. Streak
Correct Answer: D. Streak
Rationale: A streak test determines the color of a mineral in powdered form. The mineral is
dragged across an unglazed porcelain plate, producing powder that can be examined for
color. This differs from surface color, which can vary considerably because of impurities or
other causes.
Question 5
An unknown mineral scratches a glass plate. Which conclusion is most justified?
A. The mineral is harder than the glass plate.
B. The mineral must have a metallic luster.
C. The mineral must have one cleavage plane.
D. The mineral has a white streak.
,Correct Answer: A. The mineral is harder than the glass plate.
Rationale: A scratch test compares relative hardness. If the unknown mineral produces a
genuine groove in the glass, the unknown is harder than that glass surface. This observation
does not by itself establish luster, cleavage, or streak color, so additional tests are needed for
identification.
Question 6
Which mineral occupies position 7 on the Mohs hardness scale?
A. Calcite
B. Quartz
C. Fluorite
D. Orthoclase
Correct Answer: B. Quartz
Rationale: The standard Mohs sequence places talc at 1, gypsum at 2, calcite at 3, fluorite at
4, apatite at 5, orthoclase at 6, quartz at 7, topaz at 8, corundum at 9, and diamond at 10.
Quartz therefore represents hardness 7.
Question 7
A specimen has a hardness of approximately 3. Which standard mineral would be the most
appropriate reference for confirming that estimate?
A. Talc
B. Gypsum
C. Calcite
D. Quartz
Correct Answer: C. Calcite
Rationale: Calcite has a Mohs hardness of 3 and is therefore an appropriate reference
mineral for an unknown specimen suspected to have hardness near 3. Hardness testing
works by comparing whether known materials can scratch the unknown rather than simply
estimating hardness visually.
Question 8
A mineral repeatedly breaks along smooth, flat, predictable surfaces. Which property does
this behavior indicate?
, A. Streak
B. Luster
C. Fracture
D. Cleavage
Correct Answer: D. Cleavage
Rationale: Cleavage occurs when a mineral preferentially breaks along planes determined by
its internal atomic structure. Repeated, smooth, predictable breakage surfaces are
characteristic of cleavage. Fracture instead refers to breakage that does not follow consistent
cleavage planes.
Question 9
A mineral breaks irregularly without producing repeated flat planes. Which description is
most appropriate?
A. Fracture
B. Cleavage
C. Streak
D. Luster
Correct Answer: A. Fracture
Rationale: Fracture describes the way a mineral breaks when it does not follow a preferred
cleavage plane. Irregular, curved, jagged, or uneven breakage can therefore indicate
fracture. Cleavage would require consistent planar breakage related to the mineral's internal
structure.
Question 10
Which observation would be least reliable if used alone to identify an unknown mineral?
A. Cleavage
B. Color
C. Hardness
D. Streak
Correct Answer: B. Color
Rationale: Color is visually obvious but is often variable within the same mineral because of
impurities and other factors. Several different minerals may also share the same color.
Identification is therefore stronger when color is combined with hardness, streak, luster,
cleavage, crystal form, and other diagnostic properties.
IDENTIFICATIONINTRODUCTION TO GEOLOGY
AND SOCIETAL IMPACTS | COMPREHENSIVE
LABORATORY STUDY GUIDE, QUESTIONS &
ANSWERS | 2026/2027 UPDATED EDITION
PART I — Mineral Identification Fundamentals
Question 1
A student is given an unknown mineral and records that it is naturally occurring, solid,
inorganic, crystalline, and has a restricted chemical composition. Which conclusion is best?
A. It satisfies the standard definition of a mineral.
B. It must be a rock because it contains crystals.
C. It must be synthetic because its chemistry is restricted.
D. It cannot be identified without knowing its geologic age.
Correct Answer: A. It satisfies the standard definition of a mineral.
Rationale: A mineral is generally characterized as a naturally occurring, inorganic solid with
an ordered internal structure and a definite chemical composition or limited compositional
range. These criteria distinguish minerals from ordinary manufactured substances and rocks.
Identification then relies on physical and chemical properties rather than age alone.
Question 2
When comparing two unknown specimens, which observation most directly describes how
each specimen interacts with visible light?
A. Streak
B. Luster
C. Hardness
D. Cleavage
Correct Answer: B. Luster
Rationale: Luster describes the way light reflects from a mineral's surface. Common
descriptive categories include metallic, vitreous, pearly, and other nonmetallic appearances.
Streak concerns powdered color, hardness concerns scratch resistance, and cleavage
concerns preferred breakage directions, so none directly describes surface reflection.
,Question 3
A mineral appears metallic and reflective even though its streak is dark gray. Which property
is being described by the word “metallic”?
A. Hardness
B. Streak
C. Luster
D. Cleavage
Correct Answer: C. Luster
Rationale: Metallic is a luster classification describing strong, metal-like reflection from a
mineral surface. Streak describes the powder produced during a streak test, while hardness
and cleavage describe different physical behaviors. Therefore, the observation that the
specimen looks metal-like concerns luster specifically.
Question 4
A student rubs an unknown mineral across an unglazed porcelain plate and observes a fine
white powder. What property has been measured?
A. Fracture
B. Cleavage
C. Hardness
D. Streak
Correct Answer: D. Streak
Rationale: A streak test determines the color of a mineral in powdered form. The mineral is
dragged across an unglazed porcelain plate, producing powder that can be examined for
color. This differs from surface color, which can vary considerably because of impurities or
other causes.
Question 5
An unknown mineral scratches a glass plate. Which conclusion is most justified?
A. The mineral is harder than the glass plate.
B. The mineral must have a metallic luster.
C. The mineral must have one cleavage plane.
D. The mineral has a white streak.
,Correct Answer: A. The mineral is harder than the glass plate.
Rationale: A scratch test compares relative hardness. If the unknown mineral produces a
genuine groove in the glass, the unknown is harder than that glass surface. This observation
does not by itself establish luster, cleavage, or streak color, so additional tests are needed for
identification.
Question 6
Which mineral occupies position 7 on the Mohs hardness scale?
A. Calcite
B. Quartz
C. Fluorite
D. Orthoclase
Correct Answer: B. Quartz
Rationale: The standard Mohs sequence places talc at 1, gypsum at 2, calcite at 3, fluorite at
4, apatite at 5, orthoclase at 6, quartz at 7, topaz at 8, corundum at 9, and diamond at 10.
Quartz therefore represents hardness 7.
Question 7
A specimen has a hardness of approximately 3. Which standard mineral would be the most
appropriate reference for confirming that estimate?
A. Talc
B. Gypsum
C. Calcite
D. Quartz
Correct Answer: C. Calcite
Rationale: Calcite has a Mohs hardness of 3 and is therefore an appropriate reference
mineral for an unknown specimen suspected to have hardness near 3. Hardness testing
works by comparing whether known materials can scratch the unknown rather than simply
estimating hardness visually.
Question 8
A mineral repeatedly breaks along smooth, flat, predictable surfaces. Which property does
this behavior indicate?
, A. Streak
B. Luster
C. Fracture
D. Cleavage
Correct Answer: D. Cleavage
Rationale: Cleavage occurs when a mineral preferentially breaks along planes determined by
its internal atomic structure. Repeated, smooth, predictable breakage surfaces are
characteristic of cleavage. Fracture instead refers to breakage that does not follow consistent
cleavage planes.
Question 9
A mineral breaks irregularly without producing repeated flat planes. Which description is
most appropriate?
A. Fracture
B. Cleavage
C. Streak
D. Luster
Correct Answer: A. Fracture
Rationale: Fracture describes the way a mineral breaks when it does not follow a preferred
cleavage plane. Irregular, curved, jagged, or uneven breakage can therefore indicate
fracture. Cleavage would require consistent planar breakage related to the mineral's internal
structure.
Question 10
Which observation would be least reliable if used alone to identify an unknown mineral?
A. Cleavage
B. Color
C. Hardness
D. Streak
Correct Answer: B. Color
Rationale: Color is visually obvious but is often variable within the same mineral because of
impurities and other factors. Several different minerals may also share the same color.
Identification is therefore stronger when color is combined with hardness, streak, luster,
cleavage, crystal form, and other diagnostic properties.
