We've just moved into a 1908 Edwardian in San Francisco. Behind the sink was terrible wallpaper, which I removed immediately. Under that was a layer of newspaper and under that several layers of old paint.

At the bottom of all that mess is beautiful tile the color of milk glass. It is very soft though. Not soft enough to dent with a finger nail, but easy to gouge with a razor blade. What is this tile made of? Paint stripper muddled the surface of the tile so how can I safely remove the paint and restore this lovely tile?