Gemology Certification Gemology Gemstone Grading & Evaluation 3 — Questions and Answers
Question 1: What does a GIA clarity grade of 'SI2' indicate about a diamond?
- Inclusions are not visible even under magnification
- Inclusions are obvious under 10x and visible to the naked eye
- Inclusions are noticeable under 10x magnification but eye-clean (Correct answer)
- Inclusions are very difficult to see under 10x magnification
Correct answer: Inclusions are noticeable under 10x magnification but eye-clean
SI2 (Slightly Included 2) diamonds have inclusions that are easily seen under 10x magnification and may be detectable to a careful naked eye.
Question 2: Blue sapphires from Kashmir are prized for which distinctive optical quality?
- Strong color zoning
- Vivid neon-blue fluorescence
- Velvety, cornflower-blue hue caused by fine rutile silk (Correct answer)
- Intense color saturation with high transparency
Correct answer: Velvety, cornflower-blue hue caused by fine rutile silk
Kashmir sapphires are renowned for a soft, velvety blue appearance resulting from fine rutile silk needles that scatter light within the stone.
Question 3: When evaluating a colored gemstone's color, which factor carries the greatest weight in determining value?
- Transparency
- Hue
- Saturation (Correct answer)
- Tone
Correct answer: Saturation
Saturation—the intensity or purity of color—generally has the greatest impact on a colored gemstone's value because vivid, highly saturated stones command premium prices.
Question 4: Which gemstone characteristic is described by the term 'adularescence'?
- A star-like pattern of reflected light
- A billowy, floating light effect seen in moonstone (Correct answer)
- A color-change phenomenon under different light sources
- A multicolored play of color in opal
Correct answer: A billowy, floating light effect seen in moonstone
Adularescence is the soft, glowing light phenomenon seen in moonstone, caused by light scattering between alternating layers of feldspar.
Question 5: A gem grader finds a natural inclusion that looks like a small crystal within a diamond. This inclusion is classified as a:
- Feather
- Knot
- Crystal (Correct answer)
- Needle
Correct answer: Crystal
A crystal inclusion is a mineral crystal trapped within a diamond during its formation, and it is classified as such in GIA clarity grading.
Question 6: Which proportional element in a round brilliant diamond most directly affects light leakage through the pavilion?
- Table diameter percentage
- Crown height percentage
- Pavilion depth percentage (Correct answer)
- Girdle thickness
Correct answer: Pavilion depth percentage
Pavilion depth percentage is critical because if the pavilion is too shallow or too deep, light will escape through the bottom rather than reflect back through the crown.
Question 7: On the Munsell color system, 'chroma' is equivalent to which GIA-based color term?
- Hue
- Tone
- Saturation (Correct answer)
- Brilliance
Correct answer: Saturation
Munsell's 'chroma' describes the strength or purity of a color, which corresponds directly to the concept of saturation in gemological color grading.
Gemology Certification Gemology Gemstone Grading & Evaluation 3
What does a GIA clarity grade of 'SI2' indicate about a diamond?