When you work closely with opal for over 30 years, you can sometimes forget how important the most obvious questions are! In this video, I help you understand what black opal is and why it’s so valuable.
What is black opal?
It can be confusing for those not used to working with opal to see that black opal does have a riot of color! Black opal is called black because of its underlying body tone, not because it’s an entirely black gem.
The body tone of an opal refers to the opals underlying shade and the potch on the back. The darker the body tone, the blacker the opal!
Black opals sit between N1 and N4 on the body tone scale, a great guide for beginners to see where their opal sits. White and crystal opals have a lighter body tone (between N7 and N9), and dark opals sit in the middle (N5 to N6).
A black opal can only be considered a true black opal if it has the natural black potch on the back of the color bar.
Although it wouldn’t be opal if there weren’t exceptions to the rule, black crystal opals don’t have to have potch on the back. Much like the window tinting of your car, black crystal opals have a natural dark tint.
What makes Australian black opals so valuable?
Australian black opal from Lightning Ridge is valuable because it is the source of 95% of the black opal in the world. Australian opal is sedimentary, meaning it is formed in the earth, unlike black opal from elsewhere which is volcanic. Volcanic black opal is considered less stable than sedimentary opal and more likely to crack.