DCA Diamond Authentication & Certification 3 ā Questions and Answers
Question 1: What is the purpose of the AGS (American Gem Society) cut grading system's 'AGS 0' designation?
- It indicates a diamond with zero inclusions (flawless)
- It represents the Ideal cut grade ā the highest possible cut performance rating (Correct answer)
- It means the diamond has not yet been graded
- It indicates a zero-degree table facet angle
Correct answer: It represents the Ideal cut grade ā the highest possible cut performance rating
AGS uses a 0ā10 scale where AGS 0 is the best, representing an 'Ideal' cut with optimal light performance.
Question 2: Which characteristic would cause a diamond to fail authentication as a natural diamond?
- A GIA Excellent cut grade
- Growth lines consistent with high-pressure high-temperature (HPHT) synthesis (Correct answer)
- A clarity grade of SI2
- A color grade of J
Correct answer: Growth lines consistent with high-pressure high-temperature (HPHT) synthesis
HPHT-grown laboratory diamonds show distinct growth patterns (cuboctahedral or cubic) under advanced testing, distinguishing them from natural diamonds.
Question 3: What does a 'fluorescence' rating of 'Strong Blue' on a diamond report typically affect?
- The diamond's hardness on the Mohs scale
- The diamond's appearance in daylight, sometimes improving color in lower-color grades (Correct answer)
- The diamond's refractive index reading
- The diamond's carat weight measurement
Correct answer: The diamond's appearance in daylight, sometimes improving color in lower-color grades
Strong blue fluorescence can make lower-color-grade diamonds (IāM) appear whiter in daylight or fluorescent light, sometimes benefiting their appearance.
Question 4: A jeweler receives a diamond accompanied by an EGL report with a G/VS1 grade. A subsequent GIA grade might realistically show what?
- Exactly the same G/VS1 grade
- A higher color and clarity such as E/IF
- A lower color and clarity such as I/SI2, since EGL is known to grade more liberally (Correct answer)
- A carat weight discrepancy of more than 10%
Correct answer: A lower color and clarity such as I/SI2, since EGL is known to grade more liberally
EGL has historically graded more liberally than GIA by 1ā3 grades in color and clarity, meaning a GIA grade for the same stone is often lower.
Question 5: The 'plot' or 'clarity diagram' on a grading report uses different symbols. What does a red symbol typically represent?
- A surface blemish on the diamond
- An internal inclusion within the diamond (Correct answer)
- A treated area of the diamond
- A fluorescent zone in the diamond
Correct answer: An internal inclusion within the diamond
On GIA reports, red symbols on the clarity diagram represent internal characteristics (inclusions), while green symbols represent external characteristics (blemishes).
Question 6: Which testing instrument is most reliable for separating natural colorless diamonds from colorless moissanite?
- A standard diamond thermal tester (diamond selector)
- A loupe or microscope examination at 10x
- A moissanite/diamond tester that measures electrical conductivity (Correct answer)
- A UV lamp fluorescence test
Correct answer: A moissanite/diamond tester that measures electrical conductivity
Colorless moissanite is electrically conductive and passes standard thermal diamond testers as a diamond, so a specific moissanite tester measuring conductivity is required for accurate separation.
Question 7: On a GIA Full Grading Report for a round brilliant, which proportion is measured as a percentage of average girdle diameter?
- Carat weight
- Table size and total depth (Correct answer)
- Fluorescence intensity
- Polish grade
Correct answer: Table size and total depth
Table size percentage and total depth percentage on a GIA report are both expressed as percentages of the average girdle diameter.
DCA Diamond Authentication & Certification 3
What is the purpose of the AGS (American Gem Society) cut grading system's 'AGS 0' designation?