GIA DIAMONDS AND DIAMOND GRADING
FINAL EXAM NEWEST ACTUAL EXAM
COMPLETE 100+ QUESTIONS AND CORRECT
DETAILED ANSWERS PLUS RATIONALES||
LATEST UPDATE 2026
1. A diamond is composed of:
A. Silicon dioxide
B. Carbon
C. Aluminum oxide
D. Calcium carbonate
Answer: B
Rationale: Diamonds are crystalline carbon atoms bonded tetrahedrally.
2. Diamonds form under conditions of:
A. Low pressure and low temperature
B. High pressure and high temperature
C. High pressure and low temperature
D. Low pressure and high temperature
Answer: B
Rationale: Natural diamonds form deep in the Earth’s mantle under extreme conditions.
3. The typical depth of natural diamond formation is approximately:
A. 10–30 km
B. 70–90 km
C. 140–190 km
D. 300–500 km
Answer: C
Rationale: Diamonds form at depths of 140–190 km.
,4. Diamonds reach the surface primarily through:
A. Volcanic lava flows
B. River erosion
C. Kimberlite and lamproite pipes
D. Plate tectonics
Answer: C
Rationale: Kimberlite and lamproite are volcanic rocks that carry diamonds.
5. Which is NOT a diamond source rock?
A. Kimberlite
B. Lamproite
C. Basalt
D. Alluvial deposits
Answer: C
Rationale: Basalt does not host diamonds.
SECTION B: DIAMOND CRYSTAL STRUCTURE &
PROPERTIES
6. Diamond crystal system is:
A. Hexagonal
B. Trigonal
C. Cubic (isometric)
D. Orthorhombic
Answer: C
Rationale: Diamonds crystallize in the cubic system.
7. Diamond hardness on the Mohs scale is:
A. 8
B. 9
, C. 9.5
D. 10
Answer: D
Rationale: Diamond is the hardest known natural substance.
8. Diamond cleavage occurs in how many directions?
A. 2
B. 3
C. 4
D. 6
Answer: C
Rationale: Diamond has four perfect cleavage directions.
9. Diamond fracture is described as:
A. Conchoidal
B. Fibrous
C. Splintery
D. Uneven
Answer: A
Rationale: Diamonds exhibit conchoidal fracture.
10. The refractive index of diamond is approximately:
A. 1.54
B. 2.42
C. 2.65
D. 3.10
Answer: B
Rationale: Diamond has a high RI of ~2.42, contributing to brilliance.
SECTION C: OPTICAL PROPERTIES
FINAL EXAM NEWEST ACTUAL EXAM
COMPLETE 100+ QUESTIONS AND CORRECT
DETAILED ANSWERS PLUS RATIONALES||
LATEST UPDATE 2026
1. A diamond is composed of:
A. Silicon dioxide
B. Carbon
C. Aluminum oxide
D. Calcium carbonate
Answer: B
Rationale: Diamonds are crystalline carbon atoms bonded tetrahedrally.
2. Diamonds form under conditions of:
A. Low pressure and low temperature
B. High pressure and high temperature
C. High pressure and low temperature
D. Low pressure and high temperature
Answer: B
Rationale: Natural diamonds form deep in the Earth’s mantle under extreme conditions.
3. The typical depth of natural diamond formation is approximately:
A. 10–30 km
B. 70–90 km
C. 140–190 km
D. 300–500 km
Answer: C
Rationale: Diamonds form at depths of 140–190 km.
,4. Diamonds reach the surface primarily through:
A. Volcanic lava flows
B. River erosion
C. Kimberlite and lamproite pipes
D. Plate tectonics
Answer: C
Rationale: Kimberlite and lamproite are volcanic rocks that carry diamonds.
5. Which is NOT a diamond source rock?
A. Kimberlite
B. Lamproite
C. Basalt
D. Alluvial deposits
Answer: C
Rationale: Basalt does not host diamonds.
SECTION B: DIAMOND CRYSTAL STRUCTURE &
PROPERTIES
6. Diamond crystal system is:
A. Hexagonal
B. Trigonal
C. Cubic (isometric)
D. Orthorhombic
Answer: C
Rationale: Diamonds crystallize in the cubic system.
7. Diamond hardness on the Mohs scale is:
A. 8
B. 9
, C. 9.5
D. 10
Answer: D
Rationale: Diamond is the hardest known natural substance.
8. Diamond cleavage occurs in how many directions?
A. 2
B. 3
C. 4
D. 6
Answer: C
Rationale: Diamond has four perfect cleavage directions.
9. Diamond fracture is described as:
A. Conchoidal
B. Fibrous
C. Splintery
D. Uneven
Answer: A
Rationale: Diamonds exhibit conchoidal fracture.
10. The refractive index of diamond is approximately:
A. 1.54
B. 2.42
C. 2.65
D. 3.10
Answer: B
Rationale: Diamond has a high RI of ~2.42, contributing to brilliance.
SECTION C: OPTICAL PROPERTIES
