CGA CGA Diamond Grading & Gemological Science 1 — Questions and Answers
Question 1: Which of the four Cs is considered the most important factor in determining a diamond's value?
- Color
- Clarity
- Cut (Correct answer)
- Carat weight
Correct answer: Cut
Cut is considered the most important of the four Cs because it directly determines how well a diamond reflects and refracts light, affecting its overall brilliance and beauty.
Question 2: On the GIA diamond color scale, which grade represents a colorless diamond?
- A
- D (Correct answer)
- F
- Z
Correct answer: D
The GIA color scale begins at D (colorless) and runs through Z (light yellow or brown), with D being the highest and rarest color grade.
Question 3: A diamond with a 'VS2' clarity grade contains inclusions that are:
- Invisible under 10x magnification
- Very slightly difficult to see under 10x magnification (Correct answer)
- Easily visible to the naked eye
- Visible under 10x magnification but not to the naked eye
Correct answer: Very slightly difficult to see under 10x magnification
VS2 (Very Slightly Included 2) diamonds have inclusions that are minor and somewhat difficult to see under 10x magnification but are typically invisible to the naked eye.
Question 4: What is a diamond's 'fluorescence' and how does it typically affect value?
- Brilliance under natural light; increases value
- Glow under UV light; strong fluorescence often decreases value in colorless diamonds (Correct answer)
- Internal reflection pattern; always increases value
- Surface luster; has no effect on value
Correct answer: Glow under UV light; strong fluorescence often decreases value in colorless diamonds
Diamond fluorescence is the visible light emitted when exposed to UV radiation, and strong blue fluorescence in colorless to near-colorless diamonds can make them appear hazy, typically reducing their market value.
Question 5: Which diamond cutting style maximizes fire and brilliance through triangular and kite-shaped facets?
- Rose cut
- Brilliant cut (Correct answer)
- Step cut
- Single cut
Correct answer: Brilliant cut
The brilliant cut, with its 58 triangular and kite-shaped facets arranged to maximize light return, produces the greatest fire and brilliance of any cutting style.
Question 6: What does the term 'table percentage' refer to in diamond grading?
- The percentage of the diamond's weight in the table facet
- The ratio of the table facet's width to the diamond's overall diameter (Correct answer)
- The depth of the table facet relative to the crown
- The number of facets on the table
Correct answer: The ratio of the table facet's width to the diamond's overall diameter
Table percentage is the ratio of the table facet's width to the diamond's average girdle diameter, expressed as a percentage, and is a key factor in evaluating cut quality.
CGA CGA Diamond Grading & Gemological Science 1
Which of the four Cs is considered the most important factor in determining a diamond's value?