Specific Gravity of Gemstones — Reference Table
Density data for 130 gemstone species. SG min, typical, and max values sorted high to low by typical specific gravity.
Specific gravity (SG) is the ratio of a gemstone's mass to the mass of an equal volume of water. It is a dimensionless measure of density and one of the most reliable constants for gemstone identification. Unlike RI, SG can be measured on rough stones, mounted stones, and irregular fragments, making it particularly valuable when a refractometer reading is impractical.
In the field, gemologists determine SG using hydrostatic weighing — the stone is weighed in air and then in water, and the ratio gives the SG. Electronic scales with a suspension bridge attachment make this fast and accurate. Heavy liquids (such as methylene iodide at 3.32 or bromoform at 2.89) provide a quick floating/sinking test without arithmetic. For most stones, RI + SG together narrow the candidate list to one species.
High-SG stones include cassiterite (6.7–7.1), zircon (4.6–4.7), and spessartine garnet (4.12–4.20). Low-SG materials include amber (1.05–1.10), jet (1.19–1.35), and ivory (1.70–1.95). The wide overlap between similar-looking stones (e.g., various garnets, or green tourmaline vs. tsavorite) is resolved by a precise hydrostatic SG measurement combined with RI.
| Gem | SG Min | SG Typical | SG Max | Hardness | Crystal System |
|---|---|---|---|---|---|
| Cinnabar | 8.00 | 8.10 | 8.20 | 2–2.5 | Trigonal |
| Cassiterite | 6.80 | 6.95 | 7.10 | 6–7 | Tetragonal |
| Cuprite | 5.85 | 6.14 | 6.15 | 3.5–4 | Cubic |
| Cubic Zirconia | 5.60 | 5.80 | 6.00 | 8–8.5 | Cubic |
| Hematite | 4.95 | 5.28 | 5.30 | 5.5–6.5 | Trigonal |
| Zircon | 4.60 | 4.69 | 4.80 | 7.5 | Tetragonal |
| YAG | 4.50 | 4.55 | 4.60 | 8–8.5 | Cubic |
| Spessartite Garnet | 4.12 | 4.15 | 4.18 | 7–7.5 | Cubic |
| Sphalerite | 3.90 | 4.09 | 4.10 | 3.5–4 | Cubic |
| Almandine Garnet | 3.93 | 4.05 | 4.30 | 7–7.5 | Cubic |
| Star Garnet | 3.93 | 4.05 | 4.30 | 7–7.5 | Cubic |
| Color-Change Sapphire | 3.99 | 4.00 | 4.01 | 9 | Trigonal |
| Low-Type Zircon | 3.90 | 4.00 | 4.10 | 6–7.5 | Tetragonal |
| Padparadscha Sapphire | 3.95 | 4.00 | 4.03 | 9 | Trigonal |
| Pink Sapphire | 3.98 | 4.00 | 4.01 | 9 | Trigonal |
| Ruby | 3.97 | 4.00 | 4.05 | 9 | Trigonal |
| Sapphire | 3.95 | 4.00 | 4.03 | 9 | Trigonal |
| Star Ruby | 3.97 | 4.00 | 4.05 | 9 | Trigonal |
| Star Sapphire | 3.95 | 4.00 | 4.03 | 9 | Trigonal |
| Synthetic Color-Change Corundum | 3.97 | 4.00 | 4.05 | 9 | Trigonal |
| White Sapphire | 3.99 | 4.00 | 4.01 | 9 | Trigonal |
| Yellow Sapphire | 3.99 | 4.00 | 4.01 | 9 | Trigonal |
| Demantoid Garnet | 3.82 | 3.84 | 3.88 | 6.5–7 | Cubic |
| Rhodolite Garnet | 3.74 | 3.84 | 3.94 | 7–7.5 | Cubic |
| Malachite | 3.60 | 3.80 | 4.05 | 3.5–4 | Monoclinic |
| Pyrope Garnet | 3.62 | 3.78 | 3.87 | 7–7.5 | Cubic |
| Malaya / Umbalite Garnet | 3.65 | 3.75 | 3.87 | 7–7.5 | Cubic |
| Alexandrite | 3.70 | 3.73 | 3.78 | 8.5 | Orthorhombic |
| Cat's Eye Chrysoberyl | 3.70 | 3.73 | 3.78 | 8.5 | Orthorhombic |
| Chrysoberyl | 3.70 | 3.73 | 3.78 | 8.5 | Orthorhombic |
| Color-Change Garnet | 3.65 | 3.72 | 3.80 | 7–7.5 | Cubic |
| Kyanite | 3.53 | 3.68 | 3.68 | 4.5–7 | Triclinic |
| Benitoite | 3.64 | 3.66 | 3.68 | 6–6.5 | Hexagonal |
| Grossular Garnet | 3.57 | 3.61 | 3.73 | 6.5–7.5 | Cubic |
| Hessonite Garnet | 3.59 | 3.61 | 3.65 | 7–7.5 | Cubic |
| Synthetic Spinel | 3.52 | 3.61 | 3.65 | 8 | Cubic |
| Taaffeite | 3.59 | 3.61 | 3.63 | 8–8.5 | Hexagonal |
| Tsavorite Garnet | 3.59 | 3.61 | 3.65 | 7–7.5 | Cubic |
| Black Spinel | 3.58 | 3.60 | 3.61 | 8 | Cubic |
| Rhodonite | 3.57 | 3.60 | 3.76 | 5.5–6.5 | Triclinic |
| Spinel | 3.57 | 3.60 | 3.63 | 7.5–8 | Cubic |
| Sphene | 3.45 | 3.53 | 3.55 | 5–5.5 | Monoclinic |
| Topaz | 3.49 | 3.53 | 3.57 | 8 | Orthorhombic |
| Blue Diamond | 3.50 | 3.52 | 3.53 | 10 | Cubic |
| Brown Diamond | 3.51 | 3.52 | 3.53 | 10 | Cubic |
| Diamond | 3.50 | 3.52 | 3.53 | 10 | Cubic |
| Pink Diamond | 3.51 | 3.52 | 3.53 | 10 | Cubic |
| Yellow Diamond | 3.51 | 3.52 | 3.53 | 10 | Cubic |
| Rhodochrosite | 3.40 | 3.50 | 3.70 | 3.5–4 | Trigonal |
| Sinhalite | 3.47 | 3.48 | 3.50 | 6.5–7 | Orthorhombic |
| Diaspore | 3.30 | 3.35 | 3.39 | 6.5–7 | Orthorhombic |
| Tanzanite | 3.35 | 3.35 | 3.38 | 6–7 | Orthorhombic |
| Jadeite | 3.24 | 3.34 | 3.43 | 6.5–7 | Aggregate |
| Peridot | 3.27 | 3.34 | 3.48 | 6.5–7 | Orthorhombic |
| Kornerupine | 3.27 | 3.33 | 3.45 | 6.5 | Orthorhombic |
| Chrome Diopside | 3.22 | 3.30 | 3.38 | 5.5–6.5 | Monoclinic |
| Star Diopside | 3.27 | 3.29 | 3.36 | 5–6 | Monoclinic |
| Enstatite | 3.20 | 3.27 | 3.30 | 5–5.5 | Orthorhombic |
| Moissanite | 3.20 | 3.22 | 3.22 | 9.25 | Hexagonal |
| Clinohumite | 3.13 | 3.21 | 3.35 | 6 | Monoclinic |
| Apatite | 3.17 | 3.20 | 3.23 | 5 | Hexagonal |
| Thulite | 3.10 | 3.20 | 3.38 | 6–7 | Orthorhombic |
| Fluorite | 3.17 | 3.18 | 3.19 | 4 | Cubic |
| Hiddenite | 3.15 | 3.18 | 3.21 | 6.5–7 | Monoclinic |
| Kunzite | 3.15 | 3.18 | 3.21 | 6.5–7 | Monoclinic |
| Andalusite | 3.13 | 3.17 | 3.21 | 7–7.5 | Orthorhombic |
| Chrome Tourmaline | 3.00 | 3.10 | 3.20 | 7–7.5 | Trigonal |
| Green Tourmaline | 3.00 | 3.06 | 3.10 | 7–7.5 | Trigonal |
| Indicolite | 3.02 | 3.06 | 3.10 | 7–7.5 | Trigonal |
| Paraiba Tourmaline | 3.02 | 3.06 | 3.10 | 7–7.5 | Trigonal |
| Rubellite | 3.02 | 3.06 | 3.10 | 7–7.5 | Trigonal |
| Tourmaline | 3.01 | 3.06 | 3.26 | 7–7.5 | Trigonal |
| Watermelon Tourmaline | 3.00 | 3.06 | 3.10 | 7–7.5 | Trigonal |
| Danburite | 2.97 | 3.00 | 3.02 | 7–7.5 | Orthorhombic |
| Phenakite | 2.95 | 2.96 | 2.97 | 7.5–8 | Trigonal |
| Grandidierite | 2.85 | 2.95 | 2.98 | 7–7.5 | Orthorhombic |
| Nephrite | 2.90 | 2.95 | 3.03 | 6–6.5 | Aggregate |
| Prehnite | 2.82 | 2.88 | 2.94 | 6–6.5 | Orthorhombic |
| Morganite | 2.71 | 2.82 | 2.85 | 7.5–8 | Hexagonal |
| Larimar | 2.74 | 2.80 | 2.90 | 4.5–5 | Triclinic |
| Sugilite | 2.74 | 2.76 | 2.80 | 5.5–6.5 | Hexagonal |
| Turquoise | 2.60 | 2.76 | 2.90 | 5–6 | Triclinic |
| Lapis Lazuli | 2.70 | 2.75 | 2.90 | 5–6 | Aggregate |
| Pearl | 2.60 | 2.74 | 2.85 | 2.5–4.5 | Aggregate |
| Aquamarine | 2.68 | 2.72 | 2.78 | 7.5–8 | Hexagonal |
| Emerald | 2.67 | 2.72 | 2.78 | 7.5–8 | Hexagonal |
| Goshenite | 2.68 | 2.72 | 2.80 | 7.5–8 | Hexagonal |
| Heliodor | 2.68 | 2.72 | 2.74 | 7.5–8 | Hexagonal |
| Labradorite | 2.68 | 2.70 | 2.75 | 6–6.5 | Triclinic |
| Rainbow Moonstone | 2.68 | 2.70 | 2.72 | 6–6.5 | Triclinic |
| Coral | 2.60 | 2.68 | 2.70 | 3–4 | Aggregate |
| Red Beryl | 2.66 | 2.68 | 2.70 | 7.5–8 | Hexagonal |
| Amethyst | 2.63 | 2.65 | 2.65 | 7 | Trigonal |
| Ametrine | 2.63 | 2.65 | 2.67 | 7 | Trigonal |
| Aventurine | 2.64 | 2.65 | 2.69 | 7 | Trigonal |
| Citrine | 2.63 | 2.65 | 2.65 | 7 | Trigonal |
| Hawk's Eye | 2.64 | 2.65 | 2.71 | 7 | Trigonal |
| Prasiolite | 2.63 | 2.65 | 2.67 | 7 | Trigonal |
| Rock Crystal | 2.63 | 2.65 | 2.65 | 7 | Trigonal |
| Rose Quartz | 2.63 | 2.65 | 2.65 | 7 | Trigonal |
| Smoky Quartz | 2.63 | 2.65 | 2.65 | 7 | Trigonal |
| Tiger's Eye | 2.64 | 2.65 | 2.71 | 7 | Trigonal |
| Scapolite | 2.50 | 2.63 | 2.74 | 6–6.5 | Tetragonal |
| Sunstone | 2.62 | 2.63 | 2.65 | 6–6.5 | Triclinic |
| Agate | 2.58 | 2.61 | 2.64 | 6.5–7 | Trigonal |
| Bloodstone | 2.58 | 2.61 | 2.64 | 6.5–7 | Trigonal |
| Carnelian | 2.58 | 2.61 | 2.64 | 6.5–7 | Trigonal |
| Chalcedony | 2.58 | 2.61 | 2.64 | 6.5–7 | Trigonal |
| Chrysoprase | 2.58 | 2.61 | 2.64 | 6.5–7 | Trigonal |
| Onyx | 2.58 | 2.61 | 2.64 | 6.5–7 | Trigonal |
| Pietersite | 2.58 | 2.61 | 2.64 | 6.5–7 | Aggregate |
| Charoite | 2.54 | 2.60 | 2.68 | 5–6 | Monoclinic |
| Iolite | 2.57 | 2.59 | 2.66 | 7–7.5 | Orthorhombic |
| Moonstone | 2.56 | 2.58 | 2.59 | 6–6.5 | Monoclinic |
| Amazonite | 2.54 | 2.56 | 2.58 | 6–6.5 | Triclinic |
| Serpentine | 2.44 | 2.55 | 2.62 | 3–4 | Monoclinic |
| Howlite | 2.45 | 2.53 | 2.58 | 3.5 | Monoclinic |
| Variscite | 2.40 | 2.52 | 2.60 | 3.5–4.5 | Orthorhombic |
| Hauyne | 2.44 | 2.47 | 2.50 | 5.5–6 | Cubic |
| Obsidian | 2.30 | 2.40 | 2.60 | 5–5.5 | Amorphous |
| Moldavite | 2.32 | 2.35 | 2.38 | 5.5 | Amorphous |
| Hackmanite | 2.14 | 2.27 | 2.40 | 5.5–6 | Cubic |
| Sodalite | 2.14 | 2.27 | 2.40 | 5.5–6 | Cubic |
| Chrysocolla | 2.00 | 2.20 | 2.40 | 2.5–7 | Amorphous |
| Opal | 1.98 | 2.15 | 2.25 | 5.5–6.5 | Amorphous |
| Black Opal | 2.09 | 2.10 | 2.16 | 5.5–6.5 | Amorphous |
| Fire Opal | 1.98 | 2.00 | 2.20 | 5.5–6.5 | Amorphous |
| Ivory | 1.70 | 1.85 | 1.98 | 2.5–3 | Aggregate |
| Jet | 1.10 | 1.32 | 1.40 | 2.5–4 | Amorphous |
| Amber | 1.05 | 1.08 | 1.09 | 2–2.5 | Amorphous |
See also: Full Reference Database · RI Chart · UV Fluorescence Chart · Mohs Hardness Chart
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