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Design Construction for Opal and Sapphires

Here I am renewed to the forums and already asking for help. I want
to make a setting with an oval opal as the main stone surrounded
with round Sapphires. I thought I saw a formula to calculate the
number of sapphires needed to surround the opal way back but can’t
remember. I am hoping someone here can help me out with this. Not
sure on the size of the stones yet. I am trying to decide whether to
use bezel settings for the sapphires or prong settings as well. Any
help will be greatly appreciated. It’s good to be back.

Tom Timms

I thought I saw a formula to calculate the number of sapphires
needed to surround the opal 

Tom - There’s the hard way, and there’s the easy way. The hard way
is to measure an oval around the center - realize that it will be
something outside of the setting for the stone - don’t use the
girdle dimensions because that’s too close. Add the length and the
width, divide that by 2, multiply that times Pi - that’s how you get
the circumference of any oval. Then you can divide that number by
either the number of stones, which will give you the mm size of each,
or divide it by the mm, which will tell you how many. The easy way,
and what I do, is just put some stones around the oval till you get
what you want. I keep a stash of cz melee for just that purpose. Then
you can just see what you want - more of smaller, fewer of larger
stones. Also, you want to be sure you have an even number of stones -
else you will get a stone on one end and a space on the other end.
try it, you’ll see what I mean by that. Sixes will give you a stone
in the center on each of the long ends, and a space in the the center
of the short sides. Eights will give you a stone on the center line
all around.

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

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