Determine Diamond Size

[pemalon]

How does an appraiser determine the size and weight of a bezel set diamond without removing the stone and how accurate is the result?

[Tim]

The size will have to be measured with a caliper. In the case of a bezel a guestimation of what is going on behind the metal rim will have to be made.

Once the measurements have been taken weight calculation starts. The outcome is an approximate number, it is never 100% accurate due to differences in cut and measurement but it does give you a fair idea of a stone's weight.

Example:

A bezel set round brilliant cut diamond sits in the center of a ring. The diameter of the stone is 7mm. It is 6mm deep. There is formulae for each cut, the one for round brilliants is: weight = (average diameter)² X depth of stone in mm x 0.0061. So in this case that would be 7² x 6 x 0.0061= 1.79ct

[pemalon]

Thanks Tim for the explanation.