Specific Gravity Calculator
Weigh a specimen in air and again submerged in water, and get its specific gravity plus the density band it falls into — a quick, repeatable field test.
Specific gravity
Why weighing in water works
The principle dates back to Archimedes: an object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces. Water conveniently has a density very close to 1 gram per cubic centimeter, so the weight a specimen “loses” underwater equals the volume of water it displaced, in grams. Divide the specimen’s dry weight by that displaced-weight figure and the units cancel out into specific gravity — a single dimensionless number you can compare directly to published mineral values.
Denser minerals like galena or barite feel noticeably “heavy for their size” even before you do the math; the calculator just turns that intuition into a number you can check against a reference range.
Frequently Asked Questions
What is specific gravity, and why does it matter for identification?
Specific gravity (SG) is the ratio of a specimen's weight to the weight of an equal volume of water — in practice, a number equal to its density in grams per cubic centimeter. Two minerals can look almost identical in color and hardness yet have very different SGs, which makes it one of the most useful field tests once you have a scale and a way to submerge the specimen.
How does the hydrostatic (air/water) method work?
Weigh the dry specimen in air, then weigh it again while it hangs fully submerged in water (a fine thread works well, and the container should let the specimen hang freely without touching the sides). The difference between the two weights equals the weight of water the specimen displaced, and dividing the air weight by that difference gives the specific gravity directly.
What can throw the result off?
Air bubbles clinging to the specimen, a specimen that absorbs water (some are porous), a scale that isn't zeroed, or the submerged specimen touching the container all skew the reading. Tap or gently brush off bubbles before taking the submerged weight, and use the most precise scale you have — small errors matter more on small specimens.
Is specific gravity enough to identify a mineral on its own?
Rarely by itself. It's most useful combined with hardness, streak, color, and crystal habit — several minerals share a similar SG, so treat a match as narrowing the possibilities rather than confirming one.
Educational field tool only, not a certified mineral identification, gemological appraisal, or investment guidance. For a definitive ID of an unusual or valuable specimen, consult a qualified mineralogist or accredited laboratory.