GIA Diamond Proportions & Cut Analysis 2 — Questions and Answers
Question 1: What is 'brilliance' in the context of diamond light performance?
- The colored spectral light dispersed from within a diamond
- The flashes of light seen when the diamond or light source moves
- The white light reflected from the interior and exterior of a diamond (Correct answer)
- The glow produced by a diamond's fluorescence under UV light
Correct answer: The white light reflected from the interior and exterior of a diamond
Brilliance refers to the white light — both internal and external reflections — that returns to the observer's eye from a diamond.
Question 2: Which term describes the dispersion of white light into spectral rainbow colors in a diamond?
- Brilliance
- Scintillation
- Fire (Correct answer)
- Luster
Correct answer: Fire
Fire is the term for the dispersion of white light into its spectral colors as it passes through the diamond.
Question 3: How does an excessively deep (steep) pavilion angle affect the light performance of a round brilliant diamond?
- It causes light to reflect too quickly, creating excessive fire
- It causes light to leak through the pavilion sides rather than reflecting back through the crown (Correct answer)
- It makes the diamond appear larger than its actual carat weight
- It enhances scintillation by multiplying light flash points
Correct answer: It causes light to leak through the pavilion sides rather than reflecting back through the crown
An excessively steep pavilion angle redirects light out through the pavilion sides rather than totally internally reflecting it back through the crown, reducing brilliance.
Question 4: What is the 'fisheye' effect in a diamond?
- An inclusion pattern that resembles a fish eye when viewed under magnification
- A reflection of the girdle visible through the table caused by a too-shallow pavilion (Correct answer)
- The appearance of the culet when viewed face-up through the table
- A special faceting arrangement used in some fancy-shape diamonds
Correct answer: A reflection of the girdle visible through the table caused by a too-shallow pavilion
The 'fisheye' effect occurs when the pavilion angle is too shallow, causing a ring-shaped reflection of the girdle to appear through the table.
Question 5: What is 'scintillation' in diamond light performance?
- The total white light returned from a diamond's interior and exterior
- The dispersion of white light into its spectral colors
- The pattern of light and dark areas plus flashes of reflected light when the diamond or viewer moves (Correct answer)
- The brightness of a diamond's fluorescence under ultraviolet light
Correct answer: The pattern of light and dark areas plus flashes of reflected light when the diamond or viewer moves
Scintillation refers to the dynamic sparkle — the pattern of light and dark areas and the flashes of reflected light — observed when the diamond, observer, or light source moves.
Question 6: Which crown angle range is generally associated with optimal light performance in round brilliant diamonds according to GIA research?
- 15–20°
- 25–30°
- 34–35° (Correct answer)
- 40–45°
Correct answer: 34–35°
GIA research shows that crown angles between approximately 34° and 35° tend to produce optimal light performance when combined with appropriate pavilion angles.
Question 7: What does 'light leakage' indicate in a diamond cut assessment?
- Light is over-reflected from the crown facets creating glare
- Light exits through the pavilion or sides without being reflected back to the observer (Correct answer)
- Light is absorbed by internal inclusions reducing overall brightness
- Light disperses into too many spectral colors reducing white light return
Correct answer: Light exits through the pavilion or sides without being reflected back to the observer
Light leakage occurs when light exits through the pavilion or sides of the diamond rather than being totally internally reflected back through the crown, creating dark or dull areas.
GIA Diamond Proportions & Cut Analysis 2
What is 'brilliance' in the context of diamond light performance?