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Gemological tool

Hydrostatic Scale

Measures specific gravity, works even on opaque stones

Typical price$ 100 - 500
PortabilityModerately portable
Field noteNeeds stable surface

How to use it

  1. Weigh the stone dry in air and note the weight as W1
  2. Suspend the stone fully submerged in distilled water on a fine wire or hair
  3. Weigh the stone while suspended and note as W2
  4. Calculate: SG = W1 divided by (W1 minus W2)
  5. Compare to reference values for each gem species