Gemstone Quality Grading
Glossary & Reference
Understanding how gemstones are graded helps you evaluate quality and compare prices. While diamonds have standardized grading, colored gemstone evaluation is more nuanced.
Diamond Grading: The 4Cs
Cut Grade
| Grade | Description |
|---|---|
| Excellent/Ideal | Maximum brilliance and fire |
| Very Good | Nearly as brilliant, slightly lower price |
| Good | Good value, some light leakage |
| Fair | Noticeable reduction in brilliance |
| Poor | Significant light leakage |
Color Grade (White Diamonds)
| Grade | Description |
|---|---|
| D-F | Colorless - Rare and most valuable |
| G-J | Near Colorless - Excellent value |
| K-M | Faint Yellow - Visible tint |
| N-R | Very Light Yellow |
| S-Z | Light Yellow |
Clarity Grade
| Grade | Description |
|---|---|
| FL/IF | Flawless/Internally Flawless - No visible inclusions at 10x |
| VVS1/VVS2 | Very Very Slight - Difficult to see at 10x |
| VS1/VS2 | Very Slight - Visible at 10x, not eye-visible |
| SI1/SI2 | Slight Inclusions - Easy at 10x, may be eye-visible |
| I1/I2/I3 | Included - Eye-visible inclusions |
Carat Weight
1 carat = 0.2 grams = 200 milligrams
Points: 100 points = 1 carat, so 50 points = 0.50 carat
Colored Gemstone Grading
No universal standard exists, but quality is assessed by:
Color (Most Important)
- Hue - Primary and secondary colors
- Saturation - Grayish → Moderately Strong → Vivid
- Tone - Very Light → Medium → Very Dark
Ideal: Vivid saturation with medium tone
Clarity Types
| Type | Examples | Expected Clarity |
|---|---|---|
| Type I | Aquamarine, Topaz | Usually eye-clean |
| Type II | Ruby, Sapphire, Garnet | Minor inclusions acceptable |
| Type III | Emerald, Tourmaline | Inclusions almost always present |
Cut Quality
- Proportions appropriate for the gem variety
- Symmetry and polish quality
- Window (light passes through) vs. Extinction (dark areas)
- Brilliance and light return
Common Grading Systems
- GIA - Industry standard for diamonds
- AGS - Detailed cut grading
- AGL - Colored gemstone specialist
- GRS - Known for origin and color descriptions
Recording Grades in BigStash.app
Document certification grades, include photos of certificates, and track any lab reports in your item records for complete documentation.