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My biggest challenge ever! A massive chunk of Andamooka opal

What do you get when you cross a huge piece of Andamooka opal and a lot of very hard quartz? My biggest challenge ever! (literally!)

In this weeks video, we’ll work on exposing the gem inside this massive chunk of Andamooka opal.

This piece weighs 2.2 kilograms (almost 5 pounds) and it made up of opal encrusted in quartz, or quartzite or silcrete. I can see that there is a lot of color in this chunk but it’s unclear where that color meets.

I always spend time assessing the opal before taking it to the wheel and this chunk is no exception. In fact, this piece will probably take me a lot longer and require a lot more brainpower. I don’t even have a slicer big enough for this chunk so I’m going to have to be extra creative.

Where does the color run?

Before starting, I need to find out where the color runs through. To do this, I turn all of the lights off and use my x-ray vision. Just kidding, it’s only a torch. When shining a torch into the color bar, you will see that other areas of opal that are connected will glow. Using the light of the torch, you get a much clearer idea of what’s happening inside the piece and can tackle it better.

Let’s get started

I want to expose some of that color bar so I’m taking the Andmooka opal chunk to the grinder to grind back some of the edges. It doesn’t take long to realise that the hard quartzite is going to wear out my wheel if I don’t try some other techniques.

I try gouging the sand out of the edges and then move to my Dremel. The Dremel ends up being really slow as the bits are tiny and will also wear away too fast against this hard quartzite. We’re going to need another plan.

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Reassessing the challenge

After letting the piece dry out over a couple of weeks, I can see a lot of natural cracks going through the stone.

It would be a waste to cut this historic chunk of opal up, so I want to try and keep it as a whole specimen for a while before slicing it into smaller gems. This massive piece of Andamooka opal has been out of the ground and sitting in a safe for the last 60 years. It has a lot of historic value that I want to preserve for a little while longer.

A piece this big is a work in progress and a true challenge. It’s going to take some time for me to uncover the opal in the best way possible. We’ll keep you updated in future episodes but for now, back to the drawing board!