GIA Laboratory Testing & Equipment 3 — Questions and Answers
Question 1: Which GIA instrument is specifically designed to distinguish natural diamonds from HPHT-grown synthetic diamonds based on luminescence?
- DiamondView
- Presidium Duo
- GIA iD100 (Correct answer)
- Raman spectrometer
Correct answer: GIA iD100
The GIA iD100 uses short-wave UV photoluminescence to screen loose diamonds and separate naturals from synthetics for further testing.
Question 2: In the DiamondView instrument, what type of radiation is used to induce fluorescence patterns?
- Long-wave UV (365 nm)
- X-rays
- Short-wave UV below 230 nm (Correct answer)
- Visible blue light (450 nm)
Correct answer: Short-wave UV below 230 nm
The DiamondView uses very short-wave UV radiation (below 230 nm) to induce fluorescence patterns that reveal a diamond's growth structure.
Question 3: A diamond examined under the DiamondView shows a cuboctahedral fluorescence pattern. What does this indicate?
- Natural diamond with radiation treatment
- HPHT synthetic diamond (Correct answer)
- CVD synthetic diamond
- Natural diamond with no treatment
Correct answer: HPHT synthetic diamond
HPHT synthetic diamonds grow in a cuboctahedral pattern, which produces a distinctive cross or hourglass fluorescence pattern in the DiamondView.
Question 4: What characteristic fluorescence pattern does a CVD synthetic diamond typically show under the DiamondView?
- Cross-shaped cuboctahedral pattern
- Layered or striated parallel growth lines (Correct answer)
- No fluorescence at all
- Concentric ring pattern
Correct answer: Layered or striated parallel growth lines
CVD synthetic diamonds show layered, striated growth patterns reflecting the layer-by-layer deposition process used in chemical vapor deposition.
Question 5: Which piece of equipment measures the electrical conductivity of a stone to differentiate moissanite from diamond?
- Thermal conductivity probe only
- Moissanite tester (electrical tester) (Correct answer)
- Polariscope
- Spectroscope
Correct answer: Moissanite tester (electrical tester)
Dedicated moissanite testers use electrical conductivity because moissanite conducts electricity while diamond (an electrical insulator) does not.
Question 6: When using a loupe or microscope to identify CVD synthetic diamonds, which internal feature is most diagnostic?
- Pinpoint inclusions arranged in planes
- Graining lines and metallic flux inclusions
- Graphite inclusions and dark clouds
- Parallel growth planes and sometimes graining (Correct answer)
Correct answer: Parallel growth planes and sometimes graining
CVD synthetics often show parallel growth planes and internal graining, sometimes visible as banding under magnification.
Question 7: HPHT synthetic diamonds frequently contain which type of inclusion that is rarely seen in natural diamonds?
- Feathers and clouds
- Metallic flux inclusions (iron, nickel, cobalt) (Correct answer)
- Needle-like rutile crystals
- Growth tubes
Correct answer: Metallic flux inclusions (iron, nickel, cobalt)
The metal catalysts (iron, nickel, cobalt) used in HPHT synthesis can become trapped as metallic flux inclusions, sometimes appearing magnetic.
GIA Laboratory Testing & Equipment 3
Which GIA instrument is specifically designed to distinguish natural diamonds from HPHT-grown synthetic diamonds based on luminescence?