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Natural
Gemstones are used in plenty in jewellery settings. There are some useful formulas for estimating the weight of gemstones in settings. These formulas could be used where the stones cannot be removed for accurate weighing. The formulas are displayed below for your
convenience. These formulas are calculated for well proportioned stones, however 2% to 6% could be added for bulge factor i.e. excessively steep crown or pavilion angles. Also remember that the resulting weights of these formulas are approximate only, accuracy could be achieved only after correct estimation of bulge factors.
Kindly Note:
| 1. |
All weights are given in carats. |
| 2. |
All measurements are given millimeters (mm).3. An asterisk (*) indicates multiplication. |
| 3. |
A Slash (/) indicates division.5. |
| 4. |
S.G. indicates specific gravity (see individual stone descriptions for values or the
url). |
Formulas:
1. For round faceted stones:
weight = average diameter * average diameter * total depth * S.G. * .0018
2. For oval faceted stones:
average diameter = (length + width) / 2
weight = average diameter * average diameter * total depth * S.G. * .0020
3. For rectangular faceted stones:
weight = length * width * total depth * S.G. * .0026
4. For square or emerald cut faceted stones:
weight = length * width * total depth * S.G. * .0025
5. For pear shaped or heart shaped faceted stones:
weight = length * width * total depth * S.G. * .0018
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