If you have a rotary tool (Dremel, Foredom, Ray Foster high speed dental lathe or similar) and a Hazardous Dust Vacuum system, you can use this kit to dry-sand the undulating opal face from the grinder stage all the way to a pre-polish with three steps.
SILICA DUST from opal sanding is HAZARDOUS.You must use an effective hazardous dust removal system and protective breathing equipment when dry-sanding. Also take the normal precautions when using rotary tools, including protective eye-wear, no loose clothing or hair, and be aware of electrical hazards.
These are the tools I use every day to cut boulder opal, white opal and Lightning Ridge material.
The kit includes:
5 x 2.35mm shaft silicone mandrel for mounting the pads and sandpaper
10 x self adhesive rubber foam discs
2 x discs of diamond flex pads
50 discs of each grit (240/320/600/800) Hermes WS Flex 1600 silicone carbide sandpaper.
Stick the self-adhesive rubber pad to the face of the silicone mount. Use an abrasive to centre the rubber pad in the machine to eliminate vibration. All you need is some super glue to stick the sanding discs to the foam pad, centre the pad using an abrasive tool. You can slightly dull the fresh sandpaper using some scrap opal to start using the sandpaper on your opals.
I recommend using the following sequence:
1) Diamond flex pad 2) 240 grit sandpaper 3) 600 grit sandpaper - then polish as normal.
For smaller stones or thin colour bars, use 360 grit and then 800 grit before polishing.