DREMEL/ROTARY TOOL METHOD
Great low budget method to cut and polish opal but also allow for more complicated carvings and natural freeform style opals.
Carving will be forever my favorite method of processing rough opals to polished gemstones.
Here is a brief 1 minute video summarizing the entire process.
Precautions
1/ Use water at all stages as opal dust is silica and can result in silicosis if breathed in.
2/ Use a mask if you find that you are producing any dust.
3/ Wear safety glasses or use a splatter guard like I do for the YouTube channel to keep your eyes safe.
4/ Use a flex shaft attachment to avoid water or dust getting into your Dremel/rotary tool.
4/ Be cautious of grinding away your skin. Dopping the stone can help you avoid this.
5/ Take a break every now and then. The vibrations from holding the handpiece can give you a tingling feeling in your fingers after long periods of time.
Step One: Rubbing
Starting out you need to know what you've got.
Remove "potch" (no play of colour common opal) around the opal bar(s) to expose it fully, following any small glimpse you have with a metal/diamond burr, either electroplated or sintered.
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Once you've got that done you should be able to determine which side of the bar you want to fully reveal but don't go to far with the low grit! Stop just before you hit the colour or the deep scratches will be hard to remove without losing too much colour.
Step Two: Shaping
Decide on the shape you want your final stone to be and continue with the metal/diamond burr, until you are pretty happy with the shape. You should maximize the size of the stone whilst also removing any inclusions such as sand, cracks and/or potch. This is a great time to use a stencil for the perfect shape and it also helps to see the inclusions you will be removing.
Step Three: Pre-Polishing
Now that you have a rough shape you can begin the final fine tuning of your shape and begin to get to a pre-polish.
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Swap from the metal/diamond burr to a diamond pacific nova resin point. Typically I will go from a 600 grit sintered diamond burr to a 280 grit nova point. Then step up in grits from 280, 600, 1200 and finally 3000.
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Between each grit wash your stone with water and dry it! The drying part is important as you can see the progress of your hard work and you should see the scratches getting smaller and smaller. Over time you will learn what each grit's scratches look like.
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By the time you get to your highest grit the opal face should be fully revealed and shape finalized. There should be no scratches and a slight shine starting to form.
Step Four: Polishing
My fave part!!! Here you just need your choice of polishing compound which can be a metal oxide such as cerium/tin/aluminium oxide or a range of diamond pastes.
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For most opal I recommend cerium oxide, though depending on the opal other options can be slightly more effective in terms of efficiency and outcome. I have a video detailing this on the channel (https://youtu.be/IooWs2tndmo).
To use the cerium oxide powder you just need to mix up a solution then apply this to a dense felt burr. Use this on the stone until you get a shiny mirror finish and you have a finished gem!
Keep the solution and felt burr for future uses.