SG Calculation

I do see a lot of people doing SG’s the hard way using all sorts of jigs and contraptions to try and measure the weight of the stone in water. There’s a simpler way – you just need to measure the weight of the water displaced by the stone when fully immersed.

You will only need an accurate carat scale (accuracy to at least .01g), a small beaker/glass of water, a calculator and some fine cotton.

Weigh the piece of aquamarine: 2.06g
Tie some cotton to the stone, use a slip-knot, or make a little cotton sling for small cut stones.
Zero a beaker of water on the scales
Measure the weight of the water displaced by totally immersing the stone supported by cotton, just below the surface, not touching anything: 0.76g

Divide 2.06 by 0.76

Answer: 2.71

That’s it; done.

Walter Schumann Gemstones of the World says for aqua SG: 2.68 – 2.74

Bang in the middle!

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