Calculating and estimating the weight of gemstones using dimensions...........

An issue facing an appraiser/valuer is not only identifying mounted gemstones but weighing them!

These two facts are significant in determining value. Stones mounted into jewellery can make this part of appraising and valuing a little more difficult. The only way to achieve 100% accuracy is to remove the stone or stones from their mount, test them, weigh them and re-set them in the mounts from which they came. This is easier said than done requiring not only appraiser's skills but those of a 'jobbing' jeweller too. This will of course consume more time and increase costs but these are not the main concern. How practical is to un-set and re-set stones in a piece of jewellery? Unknown events, incidents or accidents may or may not lie in wait. All things considered un-setting and re-setting for this purpose should be considered a risk, a risk not worth taking!! It also makes fees a lot higher and less affordable, and the length of time to complete an appraisal becomes worryingly long for a client keen to receive back their treasured items of jewellery.

So how will we find out the weight of a gemstone in this instance? Gemmologists have developed formulae to estimate the weight of gemstones to a high degree of accuracy. It takes into account the gemstones specific gravity, shape/cut and dimensions of that shape/cut. These formulae may not calculate exact result and are subjective but in the hands of an experienced user they can give a pretty good guide as to the weight of a mounted gemstone. You should find a disclaimer within a valuations schedule notes stating the limitations of these formulas. They provide estimates not 'exact result; most importantly they mean no risk of incident or accident occurring to someone's precious item of jewellery. I have devised a couple of weight estimation programs I use to estimate the weights of diamonds and gemstones I am appraising. They are available to use just follow the instructions below.

To estimate the weight of a diamond click HERE   All you need to do is select the shape you have measured and input your dimensions (L, W, D) in the pale yellow hi-lighted boxes. (Overwrite any existing figures)

To estimate the weight of a gemstone other than diamond click HERE    Select the gemstone and the shape on the scroll down menus and then input your measured dimensions in the blank boxes.

Of course you can use the diamond estimation and convert it into another gemstones weight by dividing the result by 3.52 (specific gravity of diamond) and muliplying it by the specific gravity of the different gemstone. For example: To convert the diamond weight of 1.25 carats into a sapphire weight:-  1.25 divided by 3.52 = 0.3551 multiply by 4.00 (specific gravity of sapphire) equals 1.42 carats.