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What is an opal rub? Let’s cut two and see!

Today, I’ll explain to you what an opal rub is while cutting two of them!

By the time you’ve finished watching this video, you’ll have an answer to these questions:

  • What is an opal rub?
  • Why would miners sell their opal as a rub?
  • Why do opal rubs cost more than rough opal?

I’ve got two opal rubs that I recently bought and will be cutting, polishing, and valuing with you today.

What is an opal rub?

Besides being the sound some frogs make, a rub is a term used for a preformed opal. An opal rub is the stage between a rough and polished and has been rubbed slightly on the wheel to get some form.

Why do miners sell their opals as rubs?

Rough opal can be a risk to buy as you can never know the value of the gem until it’s cut. An opal rub has been preformed by the miner to get an idea on how many carats will come out, and what color faces the best.

For these reasons, miners can’t get the same price for their rough as they can for an opal rub.

Today’s gems

Let’s get a little background on the two opal rubs I will be cutting today.

Our first rub is a black opal from the Mintabie Opal Fields in South Australia and is seam opal. The second is a beautiful black nobby opal from Lightning Ridge.

Want to know the difference between seam opal and nobby opal? Check out one of my earlier videos here

After cutting and polishing these babies, let’s chat about how I value black opal. 

It’s essential to measure the body tone of the opal to see whether it’s in the black opal range but, after that, there are a lot of other factors that matter. The brightness, cabochon, color, and pattern of the opal are just a few of the different ways I place value on a gem.

The common misconception that the blackest body tone equals the highest price is something that I debunked in this video

The final product

I’m thrilled with the two gems I cut today! They both came out with some great color and brightness, the second being a little darker with some interesting patterns.

The first rub, our Mintabie seam opal, came in at 2.86-carats of black opal. The other, our Lightning Ridge nobby opal, produced a gem-quality 4.39-carat black opal.