Quick weight reference for popular round sizes. Note how Ruby is heavier than Emerald for the same size.
| Size | Ruby/Sapphire | Emerald | Topaz |
|---|---|---|---|
| 5.0 mm | 0.57 ct | 0.38 ct | 0.50 ct |
| 6.0 mm | 0.98 ct | 0.65 ct | 0.85 ct |
| 6.5 mm | 1.15 ct | 0.78 ct | 1.00 ct |
| 7.0 mm | 1.55 ct | 1.05 ct | 1.35 ct |
| 8.0 mm | 2.30 ct | 1.55 ct | 2.00 ct |
The S.G. value determines how heavy a stone is compared to water. A higher S.G. means a heavier gem.
| Gemstone | S.G. Value |
|---|---|
| Zircon (High) | 4.70 |
| Ruby / Sapphire | 4.00 |
| Spinel | 3.60 |
| Topaz | 3.53 |
| Emerald | 2.72 |
| Quartz | 2.65 |
| Opal | 2.15 |