Pricing opals is a bit of an art form. There are so many factors to consider. Here is a recent pricing exercise I did for 6 opals. Behind the scenes I have formulas from books to plug these numbers into, and I have my own history of opals I've already priced for comparison. I also have a few good friends in the industry who assist from time to time.
In the above image, the left hand side should read:
The main considerations for opal pricing are:
1. The TYPE of opal (Black Opal, Semi-Black, White, Crystal, Semi-Crystal)
2. The BRIGHTNESS of the stone (measured from 1 to 5)
3. The BODY TONE (how white or grey the face of the opal is) from (1 to 9).
4. The COLOR(S), Saturation and Value.
5. The PATTERN, consistency, cut, inclusions, and other smaller factors.
I've not even listed all the variables here! So you can see that pricing is tricky. I'm getting better at it, but I still have much to learn.
Contact me if you'd like to know more!