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Global Institute of Gemology • Gemology Tools
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DENSITY / CONDUCTIVITY / SPECTROSCOPY

Other Gemology Tools

Gemstone identification relies on multiple independent properties. Specific gravity, absorption spectra and conductivity tests add evidence beyond visual colour and optical character.

Spectroscope instrument, cut out from the original photographic collection

Specific gravity

Hydrostatic weighing estimates density relative to water. Accurate measurement requires care with bubbles, suspension, temperature and mounting.

Thermal and electrical conductivity

Thermal conductivity testers can help screen certain materials. Electrical conductivity is a different measurement and should not be confused with heat transfer.

Absorption spectroscopy

A hand spectroscope reveals selected absorption features. Interpret bands with the source spectrum, lighting and specimen orientation in mind.

Illustrated guide

Thermal and electrical conductivity testers — illustrated gemology guide
Thermal and electrical conductivity testers
Specific gravity · hydrostatic weighing — illustrated gemology guide
Specific gravity · hydrostatic weighing
Specific gravity · heavy liquids example — illustrated gemology guide
Specific gravity · heavy liquids example
Hand spectroscope · absorption bands — illustrated gemology guide
Hand spectroscope · absorption bands

Specific gravity calculator

Enter the mass in air and the apparent mass when the specimen is fully immersed in water, without touching the container.

Enter both measurements to calculate specific gravity.Approximation at room temperature. Assumes water density ≈ 1 g/cm³ and does not correct for suspension buoyancy.

Frequently asked questions

Is specific gravity enough to identify a gem?

No. Many materials have overlapping densities; combine it with RI, optical character and other tests.