This is how I would go about figuring out how many sapphires to

surround an opal.

First, find the circumference of the opal - add length and width,

then divide that sum by 2. Now you have the average diameter of the

opal, call it OD.

Then add the diameter of the sapphires, SD, that you wish to use to

OD. Call this result Jewelry diameter - JD. Multiply JD by 3.15 as an

approximation of pi.

The result of the multiplication is Circumference or C.

Now divide C by SD and you will get the number of sapphires that you

need to surround the opal.

If you are going to bezel set the opal and the sapphires, include

the width of the bezel in the diameter of the stone.

This will all probably yield some fractional number like 8.67. The

whole number 8 is how many sapphires you need, the fraction portion

is how much extra space you have to divide between all of the

sapphires.

You still have to allow for space to set the stones. So as John

pointed out, you are going to have to do a visual trial anyway. This

bit of arithmetic just gives you a way to figure out how many of what

size you might want to try.

Judy Hoch