Lapidary Polishing Pads and Points
To start, it may help to describe what is probably the most common polishing process.
After the stone has been properly prepared for polishing by a series of sanding steps, the polishing compound, generally a metallic oxide in powder form, is mixed in a liquid, usually water, and applied to the polishing pad.
Obsidian is a volcanic glass which often contains attractive colors and inclusions, but has a reputation as being difficult to polish, although it is fairly soft and is usually uniform in structure. When people are having problems polishing obsidian, I find it is almost always because they didn’t get the sanding done adequately before attempting to polish.
Charoite is purple calcium potassium silicate. It is usually found combined with minerals of other colors, including black (Augerine Augite), orange (Tinaksite), and transparent crystals (Microcline Feldspar). Most Charoite comes from the countries of the former Soviet Union.
I have not found it to be very heat-sensitive.
Lapidary Polishing Pads and the Proper Speeds to Spin Them
Unfortunately there just isn’t one speed that works best. The glass industry has published a lot of research work on polishing glass and they found if you can keep everything else equal, the faster the surface contacting the glass runs, the faster the polish happens.
Rhodonite, an attractive pink and white gemstone, has a structure commonly called sugary: the material has small openings that will give an “orange-peel” surface that resembles badly polished jade. It is not the same thing, however. The orange-peel on jade comes from directional dissimilar hardness, or grain structure; the voids in rhodonite are actual holes and will not polish out.
I started researching jade polishing several years ago when I took over our club shop. I could get a polish on jade, but trying to tell someone else how to do it didn’t seem to work. What I found, when I started reading, was that most authors had the same problem I had: they could do it, but the ability to someone else was hard.
Lapidary Polishing Compounds
Everyone wants to know what the “best” polishing compound is and how it is used. Unfortunately I don’t think there is a single “best”—just a better one for the stone in question, depending on your technique. But here are some of my thoughts on the subject.
Nephrite and Asbestos
Nephrite is not asbestos. The confusion arises from the fact that nephrite has the same chemical composition as one of the forms of asbestos (Actinolite).
The characteristic of asbestos that causes trouble is its ability to easily break into fine fibers that are too small to be seen by the human eye.