Gemstone Density Calculator
This calculator determines gemstone specific gravity (SG) using Archimedes' principle via the hydrostatic weighing method. Weigh the gemstone in air and then suspended in water and enter both weights. The formula SG = W(air) / (W(air) - W(water)) gives specific gravity, which is numerically equivalent to density in g/cm3. Compare your result against the GIA reference table to identify the gemstone species.
Specific gravity formula (Archimedes principle)
SG = W(air) / (W(air) - W(water))
Where W(air) is the weight of the gem in air (grams) and W(water) is the apparent weight suspended in distilled water. The denominator is the weight of water displaced, which equals the volume of the gem in cm3 (since water density = 1.000 g/cm3 at room temperature). Source: GIA Gem Reference Guide (3rd edition).
GIA gemstone specific gravity reference
| Gemstone | SG (Typical) | SG Range |
|---|---|---|
| Diamond | 3.52 | 3.50-3.53 |
| Ruby / Sapphire | 4.00 | 3.95-4.10 |
| Emerald (beryl) | 2.72 | 2.68-2.80 |
| Topaz | 3.53 | 3.49-3.57 |
| Spinel | 3.60 | 3.54-3.63 |
| Amethyst / Quartz | 2.65 | 2.64-2.66 |
| Tanzanite | 3.35 | 3.30-3.38 |
| Zircon (high) | 4.70 | 4.60-4.80 |
| Peridot | 3.34 | 3.27-3.48 |
| Garnet (pyrope) | 3.78 | 3.65-3.87 |
Gemstone density calculator: frequently asked questions
What is specific gravity for gemstones?
Specific gravity (SG) is the ratio of a gemstone's mass to the mass of an equal volume of water. It is numerically equal to density in g/cm3 (since water has a density of 1.00 g/cm3). SG is one of the most useful properties for gem identification because it is consistent for each mineral species.
How is specific gravity measured by hydrostatic weighing?
SG is determined using Archimedes' principle: weigh the gem in air (W(air)), then weigh it suspended in water (W(water)). SG = W(air) / (W(air) - W(water)). The difference (W(air) - W(water)) equals the weight of water displaced, which equals the weight of a volume of water equal to the gem's volume.
What specific gravity do common gemstones have?
Diamond 3.52, Ruby/Sapphire (corundum) 4.00, Emerald (beryl) 2.68-2.80, Amethyst/quartz 2.65, Topaz 3.53, Spinel 3.58-3.61, Garnet (pyrope) 3.65-3.87, Zircon 4.60-4.80, Tanzanite (zoisite) 3.35. Source: GIA Gem Reference Guide.
Why is specific gravity useful for gem identification?
Specific gravity is a bulk property that does not depend on the sample's size or shape. Combined with refractive index, hardness, and optical properties, it allows accurate identification of the mineral species of an unknown gem. It is particularly useful when optical testing instruments are not available.
Does treatment or inclusion content affect specific gravity?
Yes. Heavily included or fractured stones may have slightly lower SG due to air-filled voids. Glass-filling or resin impregnation can lower SG substantially. Composite or doublet stones will have an SG that is a weighted average of the component materials. For definitive identification, SG must be considered alongside other gemological properties.
Official sources
- Gemological Institute of America (GIA): GIA Gem Encyclopedia.
- GIA Gem Reference Guide (3rd edition): Standard gemological constants for specific gravity, refractive index, and hardness.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.