View Full Version : How to remove impurities from slate.

07-19-2005, 01:33 PM
Every table slate that I have ever worked with has small deposits of iron pyrite in them. They will appear as these little gold colored spots. These deposits are much harder than the surrounding material. If you try to sand over one it will create a hill. I imagine that they could also affect the tool that originally ground the slate.

I just found an easy way to get them out. I used a spring loaded center punch like this one.
It shatters the pyrite. You have to wear safety glasses to do this. The shrapnel is very tiny. Some of it will shoot out as sparks. Each punch will leave an indentation just a little larger the point of the punch. Chip it down about a 16th of an inch deep and then fill with the repair material of your choice.

07-20-2005, 05:56 AM
I would think that you could also carefully disolve the metal with an acid such as sulphuric and then clean with water. Just a thought. Chuck