Hallo, Ziv Cheng:
I tried mailing you direct because this is going to take up a bit of space and I didn't want to clog up the ganoksin group, but my mailer returned my message, so we'll try this way. I am an amateur like you, but have worked with jade for 20 years. I had problems with polishing nephrite jade at first, but learnt how to do it properly many years ago from professionals. I don't know what equipment you have, so will just tell you what to do after roughing out your cab, and if you want further please email me direct - my address as at the bottom of this page. Firstly however I suggest that you visit your local library and ask the librarian for some books on making jewellery, and on lapidary as these will give you the beginnings of how to make cabochons properly, will tell you what you need, and will put you on the right lines for other work.
NOW: having made your cab, you must sand it thoroughly. I use home-made wooden discs about 8 inches diameter, backed with 1/4 in. foam rubber. I have several with 'wet-and-dry' papers fastened to the rubber backing with a peel-off rubber cement. The papers you need are about 100grit, 200grit, 300grit and 400grit, or whatever is available near to these numbers. I assume you will know - or find out about dopping from the books - but ask me if you can't find out. The discs don't need to spin fast - about 500 revs/minute is OK but not too important though it shouldn't be too fast. Use the papers to sand your cabochons, keeping the work moving on the paper in all directions with wrist action. Then, use a magnifying glass to check that the scratches made with one paper disappear when you have used the next number, and by 400# you should get the beginnings of a shine, though far from a polish. Only when there are no scratches or marks left should you go to the next step. You will need another wooden disc now and this one should be covered with a piece of fairly thick leather, rough side outwards, and spun at the same speed - again, not too important. You will need some TIN OXIDE - try the rock shops for this, but you won't need more than about 25 grams to begin with. Take a teaspoon full of this and mix it to a thin slurry with a little water. Paint some of this on to the leather with an old, clean paintbrush. This is the polishing disc. Press very hard, even getting the cab hot - but don't melt the dopping wax! Then, presently you will feel it drag - press harder and you will see the brilliant polish come up quickly at that stage. And there you are! You can use this method on any fairly hard material, like tiger-eye, chrysoprase, agates, etc., and get an excellent, professional polish. Some folk will tel you to use alumina polishes, and I believe these work OK, but I get such a good polish with tin oxide I can't be bothered messing about with alumina. However, when you get on to jade carving, you will need diamond polishes, but this is well into your future. Concentrate on getting a good polish on cabochons at this stage. But do mail me if you want more info.
Cheers,and brilliant polishing, John Burgess (firstname.lastname@example.org)