Aluminium Oxide Gemstone Polish (<0.3 um) 50g

For harder stones (including harder types of opal) you can't go past aluminium oxide.
This powder is based on Linde A and is a pure alumina at a particle size of under 0.3 micron.
Usually around $25 per 50g.

It has a greater hardness than cerium oxide which gives it a stronger abrasive polishing action (closer to diamond paste) yet still has a chemical function for sillica based tones giving a perfect middle ground between diamond and cerium oxide polishing alternatives.
 
I discuss this in greater detail here: https://youtu.be/vAdzDCp1IO0
 
This is my #1 reccommended polishing powder for Australian Queensland boulder opal as well as other harder crystals and gemstones.

Instructions can be found on the tool instructions page (HERE), and of course, there is plenty of extra info on the youtube channel.