CDG Diamond Cutting & Polishing Standards 2 — Questions and Answers
Question 1: What is the purpose of 'bruting' in the diamond cutting process?
- To polish the table facet to a high luster
- To shape the diamond into a round outline by grinding two stones against each other (Correct answer)
- To cleave the rough crystal along its grain
- To laser-inscribe the girdle with a certificate number
Correct answer: To shape the diamond into a round outline by grinding two stones against each other
Bruting (also called girdling) creates the diamond's circular outline by spinning two diamonds against each other to abrade the girdle into shape.
Question 2: A diamond cutter chooses to 'cross' or 'block' facets during the blocking stage. What does blocking produce?
- A finished brilliant with all 58 facets polished
- The 8 main crown facets and 8 main pavilion facets, plus the table and culet (Correct answer)
- Only the 32 upper-girdle facets
- The star facets and lower-girdle facets exclusively
Correct answer: The 8 main crown facets and 8 main pavilion facets, plus the table and culet
Blocking cuts the 17 or 18 primary facets (8 crown mains, 8 pavilion mains, table, and sometimes culet) that form the diamond's basic symmetrical shape.
Question 3: In the GIA grading system, which cut grade requires that all aspects of cut—proportions, symmetry, and polish—meet the most stringent standards?
- Very Good
- Good
- Excellent (Correct answer)
- Premium
Correct answer: Excellent
GIA's Excellent cut grade is the highest, awarded only when proportions, symmetry, and polish all fall within the most favorable ranges for light performance.
Question 4: A polished diamond displays a fuzzy or indistinct reflection of the table when viewed face-up. Which polish characteristic is most likely responsible?
- Naturals on the girdle
- Lizard skin surface texture
- Burn marks from overheating the polishing wheel (Correct answer)
- Extra facets on the crown
Correct answer: Burn marks from overheating the polishing wheel
Burn marks occur when a facet is polished against the grain or with too much heat, creating a hazy, milky surface that blurs reflections.
Question 5: Which proportion is measured as the distance from the culet to the girdle plane, expressed as a percentage of average girdle diameter?
- Crown height percentage
- Table percentage
- Pavilion depth percentage (Correct answer)
- Girdle thickness percentage
Correct answer: Pavilion depth percentage
Pavilion depth percentage is the vertical distance from the culet to the girdle, divided by the average girdle diameter, and is critical to how light exits through the bottom of the stone.
Question 6: What cutting defect occurs when a polisher allows the scaif (polishing wheel) to create small parallel grooves or ridges on a facet surface?
- Polish lines (wheel marks) (Correct answer)
- Abrasion
- Cavity
- Knaat
Correct answer: Polish lines (wheel marks)
Polish lines, also called wheel marks, are fine parallel scratches or ridges left on a facet when the polishing direction or compound is incorrect.
Question 7: A princess-cut diamond with a 'French corners' design differs from a standard princess cut in which specific way?
- French corners replace the corner bezel facets with star and girdle facets, creating an X-shaped pattern at each corner (Correct answer)
- French corners add extra step-cut rows to the pavilion
- French corners eliminate the culet entirely
- French corners widen the table to over 80% of diameter
Correct answer: French corners replace the corner bezel facets with star and girdle facets, creating an X-shaped pattern at each corner
French corners feature an X-shaped facet arrangement at each corner of the square, replacing the standard corner-bezel facets for a more delicate look.
CDG Diamond Cutting & Polishing Standards 2
What is the purpose of 'bruting' in the diamond cutting process?