Specific gravity is a way to express the relative density of a gemstone. It is measured as the ratio of the density of the gemstone to the density of water. It is expressed as a number that indicates how much heavier the gemstone is compared to an equal volume of water.
Scientifically, specific gravity is defined as a ratio of the mass of a given material to the mass of an equal volume of water at 4 degrees centigrade. Most gemstone substances are two to four times denser than an equal volume of water. Specific gravities are expressed in decimal numbers, for example, 4.00 for corundum, 3.52 for diamond , and 2.72 for quartz. Zircon, one of the densest of all gemstones, may have a specific gravity as high as 4.73!
Specific gravity is an important tool in gemstone identification that is useful for the gem buyer as well as the gemologist. A 1-carat stone with higher specific gravity will be smaller than a 1-carat stone with lower specific gravity. So don't be surprised when the sapphire you buy is smaller than your diamond. That's because sapphire has a higher specific gravity. On the other hand, the 5-carat tourmaline you buy might be larger than you expected, because tourmaline has a fairly low specific gravity.
The following chart lists the specific gravity of 145 varieties of gemstones, arranged in descending order.
Cassiterite
Specific Gravity
6.7 - 7.1
Chemical Composition
Tin oxide
Crystal Structure
Tetragonal
Hematite
Specific Gravity
5.12 - 5.28
Chemical Composition
Iron oxide
Crystal Structure
Trigonal
Rainbow Pyrite
Specific Gravity
5 - 5.2
Chemical Composition
Iron sulphide
Crystal Structure
Cubic
Spessartite Garnet
Specific Gravity
4.12 - 4.18
Chemical Composition
Manganese aluminium silicate
Crystal Structure
Cubic
Smithsonite
Specific Gravity
4 - 4.65
Chemical Composition
Zinc carbonate
Crystal Structure
Trigonal
Star Ruby
Specific Gravity
3.97 - 4.05
Chemical Composition
Aluminum oxide
Crystal Structure
Trigonal
Ruby
Specific Gravity
3.97 - 4.05
Chemical Composition
Aluminum oxide
Crystal Structure
Trigonal
Color Change Sapphire
Specific Gravity
3.95 - 4.03
Chemical Composition
Aluminum oxide
Crystal Structure
Trigonal
Sapphire
Specific Gravity
3.95 - 4.03
Chemical Composition
Aluminum oxide
Crystal Structure
Trigonal
Star Sapphire
Specific Gravity
3.95 - 4.03
Chemical Composition
Aluminium oxide
Crystal Structure
Trigonal
Almandine Garnet
Specific Gravity
3.93 - 4.3
Chemical Composition
Iron aluminium silicate
Crystal Structure
Cubic
Zircon
Specific Gravity
3.93 - 4.73
Chemical Composition
Zirconium silicate
Crystal Structure
Tetragonal
Sphalerite
Specific Gravity
3.9 - 4.1
Chemical Composition
Zinc sulphide
Crystal Structure
Cubic
Rhodolite Garnet
Specific Gravity
3.85
Chemical Composition
Magnesium aluminum silicate
Crystal Structure
Cubic
Gaspeite
Specific Gravity
3.71
Chemical Composition
Nickel magnesium iron carbonate
Crystal Structure
Trigonal
Melanite
Specific Gravity
3.7 - 4.1
Chemical Composition
Calcium iron silicate
Crystal Structure
Cubic
Chrysoberyl Cat's Eye
Specific Gravity
3.7 - 3.78
Chemical Composition
Beryllium aluminium oxide
Crystal Structure
Orthorhombic
Alexandrite
Specific Gravity
3.7 - 3.78
Chemical Composition
Beryllium aluminum oxide
Crystal Structure
Orthorhombic
Azurite
Specific Gravity
3.7 - 3.9
Chemical Composition
Basic Copper Carbonate
Crystal Structure
Monoclinic
Demantoid Garnet
Specific Gravity
3.7 - 4.1
Chemical Composition
Calcium iron silicate
Crystal Structure
Cubic
Chrysoberyl
Specific Gravity
3.7 - 3.78
Chemical Composition
Beryllium aluminium oxide
Crystal Structure
Orthorhombic
Hessonite Garnet
Specific Gravity
3.64 - 3.69
Chemical Composition
Calcium aluminum silicate
Crystal Structure
Cubic
Color-Change Garnet
Specific Gravity
3.62 - 3.87
Chemical Composition
Magnesium aluminum silicate
Crystal Structure
Cubic
Pyrope Garnet
Specific Gravity
3.62 - 3.87
Chemical Composition
Magnesiium aluminum silicate
Crystal Structure
Cubic
Star Garnet
Specific Gravity
3.62 - 3.87
Chemical Composition
Iron aluminum silicate
Crystal Structure
Rhombic
Grossularite Garnet
Specific Gravity
3.57 - 3.73
Chemical Composition
Calcium aluminum silicate
Crystal Structure
Cubic
Mali Garnet
Specific Gravity
3.57 - 3.73
Chemical Composition
Calcium aluminum silicate
Crystal Structure
Cubic
Tsavorite Garnet
Specific Gravity
3.57 - 3.73
Chemical Composition
Calcium aluminum silicate
Crystal Structure
Rhombic
Spinel
Specific Gravity
3.54 - 3.63
Chemical Composition
Magnesium aluminium oxide
Crystal Structure
Cubic
Kyanite
Specific Gravity
3.53 - 3.7
Chemical Composition
Aluminum silicate
Crystal Structure
Triclinic
Sphene
Specific Gravity
3.52 - 3.54
Chemical Composition
Calcium titanium silicate
Crystal Structure
Monoclinic
Diamond
Specific Gravity
3.5 - 3.53
Chemical Composition
Carbon
Crystal Structure
Cubic
Topaz
Specific Gravity
3.49 - 3.57
Chemical Composition
Aluminum fluosilicate
Crystal Structure
Orthorhombic
Mystic Topaz
Specific Gravity
3.49 - 3.57
Chemical Composition
Aluminum fluosilicate
Crystal Structure
Orthorhombic
Imperial Topaz
Specific Gravity
3.49 - 3.57
Chemical Composition
Aluminum fluosilicate
Crystal Structure
Orthorhombic
Azotic Topaz
Specific Gravity
3.49 - 3.57
Chemical Composition
Aluminum fluosilicate
Crystal Structure
Orthorhombic
Rutile Topaz
Specific Gravity
3.49 - 3.57
Chemical Composition
Aluminum fluorsilicate
Crystal Structure
Orthorhombic
Rhodochrosite
Specific Gravity
3.45 - 3.7
Chemical Composition
Manganese carbonate
Crystal Structure
Trigonal
Rhodonite
Specific Gravity
3.4 - 3.74
Chemical Composition
Manganese silicate
Crystal Structure
Triclinic
Ruby in Zoisite
Specific Gravity
3.35
Chemical Composition
Rock containing zoisite, ruby and hornblende
Crystal Structure
Orthorhombic
Tanzanite
Specific Gravity
3.35
Chemical Composition
Calcium aluminium silicate
Crystal Structure
Orthorhombic
Idocrase
Specific Gravity
3.32 - 3.47
Chemical Composition
Complex calcium aluminum silicate
Crystal Structure
Tetragonal
Cat's Eye Diaspore
Specific Gravity
3.3 - 3.39
Chemical Composition
Hydrated aluminum oxide
Crystal Structure
Orthorhombic
Hemimorphite
Specific Gravity
3.3 - 3.5
Chemical Composition
Hydrous basic zinc silicate
Crystal Structure
Orthorhombic
Color Change Diaspore
Specific Gravity
3.3 - 3.39
Chemical Composition
Hydrated aluminum oxide
Crystal Structure
Orthorhombic
Peridot
Specific Gravity
3.28 - 3.48
Chemical Composition
Magnesium iron silicate
Crystal Structure
Orthorhombic
Axinite
Specific Gravity
3.26 - 3.36
Chemical Composition
Calcium aluminum borate silicate
Crystal Structure
Triclinic
Dumortierite Quartz
Specific Gravity
3.26 - 3.41
Chemical Composition
Aluminum borate silicate intergrown with quartz
Crystal Structure
Orthorhombic
Malachite
Specific Gravity
3.25 - 4.1
Chemical Composition
Basic copper carbonate
Crystal Structure
Monoclinic
Sillimanite Cat's Eye
Specific Gravity
3.23
Chemical Composition
Aluminum silicate
Crystal Structure
Orthorhombic
Chrome Diopside
Specific Gravity
3.22 - 3.38
Chemical Composition
Calcium magnesium silicate
Crystal Structure
Monoclinic
Tashmarine Diopside
Specific Gravity
3.22 - 3.38
Chemical Composition
Calcium magnesium silicate
Crystal Structure
Monoclinic
Star Diopside
Specific Gravity
3.22 - 3.38
Chemical Composition
Calcium manganese silicate
Crystal Structure
Monoclinic
Hiddenite
Specific Gravity
3.17 - 3.19
Chemical Composition
Lithium aluminum silicate
Crystal Structure
Monoclinic
Apatite
Specific Gravity
3.16 - 3.23
Chemical Composition
Basic fluoro- and chloro-calicum phosphate
Crystal Structure
Hexagonal
Cat's Eye Apatite
Specific Gravity
3.16 - 3.23
Chemical Composition
Basic fluoro- and chloro-calicum phosphate
Crystal Structure
Hexagonal
Spodumene
Specific Gravity
3.15 - 3.21
Chemical Composition
Lithium aluminum silicate
Crystal Structure
Monoclinic
Kunzite
Specific Gravity
3.15 - 3.21
Chemical Composition
Lithium aluminum silicate
Crystal Structure
Monoclinic
Clinohumite
Specific Gravity
3.13 - 3.75
Chemical Composition
Magnesium silicate
Crystal Structure
Monoclinic
Andalusite
Specific Gravity
3.05 - 3.2
Chemical Composition
Aluminium silicate
Crystal Structure
Orthorhombic
Fluorite
Specific Gravity
3 - 3.25
Chemical Composition
Calcium fluoride
Crystal Structure
Cubic
Nuummite
Specific Gravity
3
Chemical Composition
Rock containing gedrite and anthophyllite
Crystal Structure
Lamellar fibrous structure
Danburite
Specific Gravity
2.97 - 3.03
Chemical Composition
Calcium boric silicate
Crystal Structure
Orthorhombic
Jadeite
Specific Gravity
2.9 - 3.03
Chemical Composition
Basic calcium magnesium iron silicate
Crystal Structure
Monoclinic
Nephrite Jade
Specific Gravity
2.9 - 3.03
Chemical Composition
Calcium magnesium iron silicate
Crystal Structure
Monoclinic
Tourmaline
Specific Gravity
2.83 - 3.32
Chemical Composition
Silicate compounded with aluminium, iron, magnesium, sodium, lithium or potassium
Crystal Structure
Trigonal
Chrome Tourmaline
Specific Gravity
2.82 - 3.32
Chemical Composition
Silicate compounded with aluminium, iron, magnesium, sodium, lithium or potassium
Crystal Structure
Trigonal
Prehnite
Specific Gravity
2.82 - 2.94
Chemical Composition
Basic calcium aluminum silicate
Crystal Structure
Orthorhombic
Paraiba Tourmaline
Specific Gravity
2.82 - 3.32
Chemical Composition
Silicate compounded with aluminium, iron, magnesium, sodium, lithium or potassium
Crystal Structure
Trigonal
Cat's Eye Tourmaline
Specific Gravity
2.82 - 3.32
Chemical Composition
Silicate compounded with aluminium, iron, magnesium, sodium, lithium or potassium
Crystal Structure
Trigonal
Lepidolite
Specific Gravity
2.8 - 2.9
Chemical Composition
Potassium lithium aluminum fluoro-silicate
Crystal Structure
Monoclinic
Verdite
Specific Gravity
2.76 - 3
Chemical Composition
Serpentine rock
Crystal Structure
Monoclinic
Sugilite
Specific Gravity
2.76 - 2.8
Chemical Composition
Potassium sodium lithium iron manganese aluminium
Crystal Structure
Hexagonal
Ammolite
Specific Gravity
2.75 - 2.8
Chemical Composition
Mainly aragonite (with calcite, silica and pyrite)
Crystal Structure
Amorphous
Larimar
Specific Gravity
2.74 - 2.88
Chemical Composition
Hydrated sodium calcium silicate with manganese
Crystal Structure
Triclinic
Calcite
Specific Gravity
2.69 - 2.71
Chemical Composition
Calcium carbonate
Crystal Structure
Trigonal
Aquamarine
Specific Gravity
2.68 - 2.74
Chemical Composition
Aluminium beryllium silicate
Crystal Structure
Hexagonal
Cat's Eye Aquamarine
Specific Gravity
2.68 - 2.74
Chemical Composition
Aluminum beryllium silicate
Crystal Structure
Hexagonal
Beryl
Specific Gravity
2.67 - 2.78
Chemical Composition
Aluminium beryllium silicate
Crystal Structure
Hexagonal
Emerald
Specific Gravity
2.67 - 2.78
Chemical Composition
Aluminium beryllium silicate
Crystal Structure
Hexagonal
Goshenite
Specific Gravity
2.66 - 2.87
Chemical Composition
Aluminum beryllium silicate
Crystal Structure
Hexagonal
Andesine Labradorite
Specific Gravity
2.66 - 2.68
Chemical Composition
Sodium calcium aluminum silicate
Crystal Structure
Triclinic
Morganite
Specific Gravity
2.66 - 2.87
Chemical Composition
Aluminium beryllium silicate
Crystal Structure
Hexagonal
Amethyst
Specific Gravity
2.65
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Rose Quartz
Specific Gravity
2.65
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Ametrine
Specific Gravity
2.65
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Citrine
Specific Gravity
2.65
Chemical Composition
Silicon dioxide
Crystal Structure
Hexagonal
Quartz Cat's Eye
Specific Gravity
2.65
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Rutile Quartz
Specific Gravity
2.65
Chemical Composition
Silicon dioxide with titanium inclusions
Crystal Structure
Trigonal
Onyx
Specific Gravity
2.65 - 2.91
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Smoky Quartz
Specific Gravity
2.65
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Strawberry Quartz
Specific Gravity
2.65
Chemical Composition
Silicon dioxide with iron oxide inclusions
Crystal Structure
Trigonal
Mystic Quartz
Specific Gravity
2.65
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Quartz
Specific Gravity
2.65
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Labradorite
Specific Gravity
2.65 - 2.75
Chemical Composition
Sodium calcium aluminum silicate
Crystal Structure
Triclinic
Aventurine
Specific Gravity
2.64 - 2.69
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Star Sunstone
Specific Gravity
2.62 - 2.65
Chemical Composition
Sodium calcium aluminum silicate
Crystal Structure
Triclinic
Sunstone
Specific Gravity
2.62 - 2.65
Chemical Composition
Sodium calcium aluminium silicate
Crystal Structure
Triclinic
Pietersite
Specific Gravity
2.6
Chemical Composition
Silicon dioxide
Crystal Structure
Aggregate
Agate
Specific Gravity
2.6 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Fossil Coral
Specific Gravity
2.6 - 2.7
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Pearl
Specific Gravity
2.6 - 2.85
Chemical Composition
Calcium carbonate
Crystal Structure
Orthorhombic
Coral
Specific Gravity
2.6 - 2.7
Chemical Composition
Calcium carbonate
Crystal Structure
Trigonal
Agate Geode
Specific Gravity
2.6 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Chrysoprase
Specific Gravity
2.58 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Iolite
Specific Gravity
2.58 - 2.66
Chemical Composition
Magnesium aluminum silicate
Crystal Structure
Orthorhombic
Tiger's Eye Matrix
Specific Gravity
2.58 - 2.64
Chemical Composition
Rock containing layers of quartz and iron oxide
Crystal Structure
Trigonal
Dendritic Agate
Specific Gravity
2.58 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Fire Agate
Specific Gravity
2.58 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Chalcedony
Specific Gravity
2.58 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Star Rose Quartz
Specific Gravity
2.58 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Hexagonal
Peanut Wood
Specific Gravity
2.58 - 2.91
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Carnelian
Specific Gravity
2.58 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Bloodstone
Specific Gravity
2.58 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Tiger's Eye
Specific Gravity
2.58 - 2.64
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Scapolite
Specific Gravity
2.57 - 2.74
Chemical Composition
Sodium calcium aluminium silicate
Crystal Structure
Tetragonal
Cat's Eye Scapolite
Specific Gravity
2.57 - 2.74
Chemical Composition
Sodium calcium aluminum silicate
Crystal Structure
Tetragonal
Amazonite
Specific Gravity
2.56 - 2.58
Chemical Composition
Potassium aluminum silicate
Crystal Structure
Triclinic
Orthoclase
Specific Gravity
2.56 - 2.58
Chemical Composition
Potassium aluminum silicate
Crystal Structure
Monoclinic
Rainbow Moonstone
Specific Gravity
2.56 - 2.59
Chemical Composition
Potassium aluminum silicate
Crystal Structure
Monoclinic
Star Moonstone
Specific Gravity
2.56 - 2.59
Chemical Composition
Potassium aluminum silicate
Crystal Structure
Monoclinic
Moonstone
Specific Gravity
2.56 - 2.59
Chemical Composition
Potassium aluminum silicate
Crystal Structure
Monoclinic
Seraphinite
Specific Gravity
2.55 - 2.75
Chemical Composition
Magnesium iron aluminum silicate hyroxide
Crystal Structure
Monoclinic
Charoite
Specific Gravity
2.54 - 2.78
Chemical Composition
Complex silicate containing phosphorus, calcium and sodium
Crystal Structure
Monoclinic
Lapis Lazuli
Specific Gravity
2.5 - 3
Chemical Composition
Sodium calcium aluminum silicate
Crystal Structure
Cubic
Maw-Sit-Sit
Specific Gravity
2.5 - 3.5
Chemical Composition
Rock containing variable amounts of kosmochlor, jadeite and albite
Crystal Structure
Monoclinic, prismatic
Jasper
Specific Gravity
2.5 - 2.9
Chemical Composition
Silicon dioxide
Crystal Structure
Trigonal
Howlite
Specific Gravity
2.45 - 2.58
Chemical Composition
Calcium borosilicate hydroxide
Crystal Structure
Monoclinic
Serpentine
Specific Gravity
2.44 - 2.62
Chemical Composition
Basic magnesium silicate
Crystal Structure
Microcrystalline
Variscite
Specific Gravity
2.42 - 2.58
Chemical Composition
Hydrous aluminum phosphate
Crystal Structure
Orthorhombic
Hambergite
Specific Gravity
2.35
Chemical Composition
Beryllium borate
Crystal Structure
Orthorhombic
Obsidian
Specific Gravity
2.35 - 2.6
Chemical Composition
Siliceous glassy rock
Crystal Structure
Amorphous
Snowflake Obsidian
Specific Gravity
2.35 - 2.6
Chemical Composition
Siliceous glassy rock
Crystal Structure
Amorphous
Moldavite
Specific Gravity
2.32 - 2.38
Chemical Composition
Silicon dioxide + aluminum oxide
Crystal Structure
Amorphous
Turquoise
Specific Gravity
2.31 - 2.84
Chemical Composition
Hydrated copper aluminum phosphate
Crystal Structure
Triclinic
Rubellite Tourmaline
Specific Gravity
2.28 - 3.32
Chemical Composition
Silicate compounded with aluminium, iron, magnesium, sodium, lithium or potassium
