DIAMOND & DIAMOND GRADING FINAL EXAM Actual
Exam Complete Questions and Answers Detailed
Rationales Pass Guaranteed - A+ Graded
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SECTION 1: DIAMOND FORMATION, MINING & ROUGH DIAMOND CHARACTERISTICS
Q1 – Q10
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Question 1 of 50
A geologist examining a rough diamond crystal recovered from a kimberlite pipe in
Botswana observes that the crystal displays a distinct octahedral habit with visible
trigons on the surface. She also notes that the diamond contains small garnet
inclusions that appear to be mantle-derived. Based on these observations, which
geological origin is most consistent with this rough diamond?
A. Alluvial deposit formed by secondary weathering of surface rocks
B. Primary kimberlite source from the upper mantle at depths exceeding 140 km ✓
CORRECT
C. Metamorphic origin from subducted oceanic crust at shallow depths
D. Impact-related formation from a meteorite collision site
Correct Answer: B
Rationale: Octahedral crystal habit with trigons and mantle-derived garnet inclusions are
definitive indicators of primary kimberlite origin from the upper mantle, where diamonds
form under high pressure and temperature conditions typically exceeding 140 km depth.
Option A describes secondary deposits where rough diamonds lose their primary crystal
features through transport and abrasion. In practice, the presence of mantle mineral
,inclusions like garnet, olivine, or clinopyroxene is how geologists confirm a diamond's
deep-earth origin and distinguish it from rare shallow-formed or synthetic stones.
Question 2 of 50
A rough diamond buyer is evaluating a parcel of stones from the Argyle mine in Western
Australia. He notices that several crystals show a distinctive brownish body color and
flattened macle shapes rather than typical octahedra. Which formation characteristic
best explains these rough diamond properties?
A. High nitrogen content in Type Ia diamonds causing brown coloration
B. Plastic deformation during rapid transport to the surface creating brown color and
macle shapes ✓ CORRECT
C. High boron content typical of Type IIb diamonds from this region
D. Graphitization of the crystal surface due to prolonged surface exposure
Correct Answer: B
Rationale: Argyle diamonds are well-documented for brown coloration caused by plastic
deformation during rapid kimberlite eruption, and the flattened macle shapes result
from resorption processes during this violent transport to the surface. Option A
incorrectly attributes the brown color to nitrogen, which typically produces yellow tones
in Type Ia diamonds, not brown. Rough buyers working with Argyle parcels learn to
expect these deformation-related characteristics, which significantly affect how the
rough is planned and cut for maximum value recovery.
Question 3 of 50
A diamond miner in the Venetia mine in South Africa extracts a rough crystal weighing
45 carats with a dodecahedral shape, smooth rounded surfaces, and a slightly greasy
luster. Under magnification, he observes that the crystal has a transparent to
translucent appearance with some internal fracturing. Which interpretation of this rough
diamond's characteristics is most accurate?
,A. The dodecahedral shape indicates this is a synthetic diamond grown by the HPHT
method
B. The rounded surfaces and dodecahedral form are typical of resorbed natural
diamonds from primary kimberlite deposits ✓ CORRECT
C. The greasy luster suggests surface contamination from mining equipment
D. The internal fracturing proves this crystal was damaged during blasting operations
Correct Answer: B
Rationale: Dodecahedral forms with rounded, resorbed surfaces are classic
morphologies for natural diamonds that have undergone dissolution during kimberlite
transport; the greasy luster is a natural optical property of diamond surfaces. Option A
is incorrect because HPHT synthetics typically show cubic-octahedral habits with
metallic flux inclusions, not dodecahedral resorption features. Experienced rough
sorters use crystal morphology as a first-line indicator of natural versus synthetic origin
before moving to more advanced testing.
Question 4 of 50
A gemologist examining a rough diamond under a binocular microscope notices a
series of parallel, triangular etch pits on the octahedral faces. These etch pits are
oriented in the same crystallographic direction and appear to be natural rather than
artificially induced. What do these features indicate about the diamond's geological
history?
A. The diamond was artificially etched with acid to improve its clarity appearance
B. The trigons are natural dissolution features formed during kimberlite transport and
indicate a natural origin ✓ CORRECT
C. The pits are polishing marks left by previous cutting attempts
D. The features are growth patterns indicating rapid crystal formation
Correct Answer: B
Rationale: Natural trigons are dissolution features with a characteristic orientation
aligned to crystallographic axes, formed during the diamond's residence in kimberlite
, magma; their presence strongly supports natural origin. Option A is incorrect because
acid etching produces irregular, non-oriented pits that lack the geometric precision of
natural trigons. Trigons are one of the first features gemologists examine when
assessing rough because they are difficult to replicate artificially and provide immediate
confidence in natural origin.
Question 5 of 50
A mining engineer is assessing the economic viability of a new kimberlite pipe
discovery. The pipe contains diamonds, but the average rough stone size is small and
the grade is low compared to established mines. However, the diamonds show
exceptional clarity and colorless to near-colorless body color. Which factor should most
influence the decision to develop this deposit?
A. The small average stone size makes the deposit economically unviable regardless of
quality
B. The exceptional clarity and color of the diamonds may command premium prices
that offset lower grade and smaller size ✓ CORRECT
C. The colorless appearance indicates the diamonds are likely synthetic and not worth
mining
D. The low grade means the deposit should be immediately abandoned in favor of
alluvial sources
Correct Answer: B
Rationale: Diamond mining economics depend on the interplay of grade, size
distribution, and quality; high-clarity, colorless stones from small but consistent pipes
can be profitable if market prices for quality offset volume limitations. Option A is overly
simplistic because many profitable mines operate on low grade but high quality, such as
some Canadian deposits. Mining feasibility studies always model price scenarios using
actual rough sample quality data rather than relying solely on carat-per-tonne figures.
Question 6 of 50
Exam Complete Questions and Answers Detailed
Rationales Pass Guaranteed - A+ Graded
══════════════════════════════════════
SECTION 1: DIAMOND FORMATION, MINING & ROUGH DIAMOND CHARACTERISTICS
Q1 – Q10
══════════════════════════════════════
Question 1 of 50
A geologist examining a rough diamond crystal recovered from a kimberlite pipe in
Botswana observes that the crystal displays a distinct octahedral habit with visible
trigons on the surface. She also notes that the diamond contains small garnet
inclusions that appear to be mantle-derived. Based on these observations, which
geological origin is most consistent with this rough diamond?
A. Alluvial deposit formed by secondary weathering of surface rocks
B. Primary kimberlite source from the upper mantle at depths exceeding 140 km ✓
CORRECT
C. Metamorphic origin from subducted oceanic crust at shallow depths
D. Impact-related formation from a meteorite collision site
Correct Answer: B
Rationale: Octahedral crystal habit with trigons and mantle-derived garnet inclusions are
definitive indicators of primary kimberlite origin from the upper mantle, where diamonds
form under high pressure and temperature conditions typically exceeding 140 km depth.
Option A describes secondary deposits where rough diamonds lose their primary crystal
features through transport and abrasion. In practice, the presence of mantle mineral
,inclusions like garnet, olivine, or clinopyroxene is how geologists confirm a diamond's
deep-earth origin and distinguish it from rare shallow-formed or synthetic stones.
Question 2 of 50
A rough diamond buyer is evaluating a parcel of stones from the Argyle mine in Western
Australia. He notices that several crystals show a distinctive brownish body color and
flattened macle shapes rather than typical octahedra. Which formation characteristic
best explains these rough diamond properties?
A. High nitrogen content in Type Ia diamonds causing brown coloration
B. Plastic deformation during rapid transport to the surface creating brown color and
macle shapes ✓ CORRECT
C. High boron content typical of Type IIb diamonds from this region
D. Graphitization of the crystal surface due to prolonged surface exposure
Correct Answer: B
Rationale: Argyle diamonds are well-documented for brown coloration caused by plastic
deformation during rapid kimberlite eruption, and the flattened macle shapes result
from resorption processes during this violent transport to the surface. Option A
incorrectly attributes the brown color to nitrogen, which typically produces yellow tones
in Type Ia diamonds, not brown. Rough buyers working with Argyle parcels learn to
expect these deformation-related characteristics, which significantly affect how the
rough is planned and cut for maximum value recovery.
Question 3 of 50
A diamond miner in the Venetia mine in South Africa extracts a rough crystal weighing
45 carats with a dodecahedral shape, smooth rounded surfaces, and a slightly greasy
luster. Under magnification, he observes that the crystal has a transparent to
translucent appearance with some internal fracturing. Which interpretation of this rough
diamond's characteristics is most accurate?
,A. The dodecahedral shape indicates this is a synthetic diamond grown by the HPHT
method
B. The rounded surfaces and dodecahedral form are typical of resorbed natural
diamonds from primary kimberlite deposits ✓ CORRECT
C. The greasy luster suggests surface contamination from mining equipment
D. The internal fracturing proves this crystal was damaged during blasting operations
Correct Answer: B
Rationale: Dodecahedral forms with rounded, resorbed surfaces are classic
morphologies for natural diamonds that have undergone dissolution during kimberlite
transport; the greasy luster is a natural optical property of diamond surfaces. Option A
is incorrect because HPHT synthetics typically show cubic-octahedral habits with
metallic flux inclusions, not dodecahedral resorption features. Experienced rough
sorters use crystal morphology as a first-line indicator of natural versus synthetic origin
before moving to more advanced testing.
Question 4 of 50
A gemologist examining a rough diamond under a binocular microscope notices a
series of parallel, triangular etch pits on the octahedral faces. These etch pits are
oriented in the same crystallographic direction and appear to be natural rather than
artificially induced. What do these features indicate about the diamond's geological
history?
A. The diamond was artificially etched with acid to improve its clarity appearance
B. The trigons are natural dissolution features formed during kimberlite transport and
indicate a natural origin ✓ CORRECT
C. The pits are polishing marks left by previous cutting attempts
D. The features are growth patterns indicating rapid crystal formation
Correct Answer: B
Rationale: Natural trigons are dissolution features with a characteristic orientation
aligned to crystallographic axes, formed during the diamond's residence in kimberlite
, magma; their presence strongly supports natural origin. Option A is incorrect because
acid etching produces irregular, non-oriented pits that lack the geometric precision of
natural trigons. Trigons are one of the first features gemologists examine when
assessing rough because they are difficult to replicate artificially and provide immediate
confidence in natural origin.
Question 5 of 50
A mining engineer is assessing the economic viability of a new kimberlite pipe
discovery. The pipe contains diamonds, but the average rough stone size is small and
the grade is low compared to established mines. However, the diamonds show
exceptional clarity and colorless to near-colorless body color. Which factor should most
influence the decision to develop this deposit?
A. The small average stone size makes the deposit economically unviable regardless of
quality
B. The exceptional clarity and color of the diamonds may command premium prices
that offset lower grade and smaller size ✓ CORRECT
C. The colorless appearance indicates the diamonds are likely synthetic and not worth
mining
D. The low grade means the deposit should be immediately abandoned in favor of
alluvial sources
Correct Answer: B
Rationale: Diamond mining economics depend on the interplay of grade, size
distribution, and quality; high-clarity, colorless stones from small but consistent pipes
can be profitable if market prices for quality offset volume limitations. Option A is overly
simplistic because many profitable mines operate on low grade but high quality, such as
some Canadian deposits. Mining feasibility studies always model price scenarios using
actual rough sample quality data rather than relying solely on carat-per-tonne figures.
Question 6 of 50
