DCA Diamond Grading & Classification 3 — Questions and Answers
Question 1: A diamond exhibits strong blue fluorescence. Under normal lighting conditions, this most commonly makes the diamond appear:
- More yellowish
- Slightly whiter or milky (Correct answer)
- More greenish
- Darker and less transparent
Correct answer: Slightly whiter or milky
Strong blue fluorescence can make a lower-color diamond appear whiter in daylight but may cause a milky or hazy appearance in some stones.
Question 2: Which diamond shape is cut to maximize carat weight retention from an octahedral rough crystal?
- Princess cut (Correct answer)
- Round brilliant
- Pear shape
- Marquise
Correct answer: Princess cut
The princess cut (square modified brilliant) is specifically designed to retain more weight from an octahedral rough crystal than a round brilliant.
Question 3: In diamond grading, the term 'twinning wisps' refers to:
- Parallel growth planes visible as flat inclusions
- Inclusions formed along irregular crystal growth disturbances (Correct answer)
- Surface scratches from polishing
- Clouds of very tiny pinpoints
Correct answer: Inclusions formed along irregular crystal growth disturbances
Twinning wisps are series of pinpoints, clouds, or crystals arranged along a twinning plane caused by irregular crystal growth.
Question 4: What GIA polish grade indicates that polish features are not visible under 10x magnification but are detectable under higher magnification?
- Excellent (Correct answer)
- Very Good
- Good
- Fair
Correct answer: Excellent
An Excellent polish grade means no polish features are detectable under 10x magnification, making the surface virtually perfect at standard grading magnification.
Question 5: A customer asks about a diamond with an 'I' clarity grade. Which best describes this stone?
- Internally Flawless with no surface blemishes
- Slightly included with minor inclusions
- Included with inclusions visible to the naked eye (Correct answer)
- Very slightly included under magnification only
Correct answer: Included with inclusions visible to the naked eye
The I1, I2, and I3 clarity grades represent 'Included' diamonds with inclusions that are obvious under 10x and may affect transparency or brilliance.
Question 6: Which measurement is used to calculate a round brilliant diamond's table percentage?
- Table diameter divided by crown height × 100
- Table diameter divided by average girdle diameter × 100 (Correct answer)
- Crown angle divided by pavilion angle × 100
- Culet size divided by table diameter × 100
Correct answer: Table diameter divided by average girdle diameter × 100
Table percentage equals the table facet's diameter divided by the diamond's average girdle diameter, multiplied by 100.
Question 7: The AGS cut grading system uses a numerical scale rather than descriptive words. What number represents the ideal cut?
- 10
- 1
- 0 (Correct answer)
- 5
Correct answer: 0
The American Gem Society (AGS) grades cut from 0 to 10, where 0 is Ideal (best) and 10 is Poor.
DCA Diamond Grading & Classification 3
A diamond exhibits strong blue fluorescence.
Under normal lighting conditions, this most commonly makes the diamond appear: