Tile – How to polish a marble table top

Depends on what the table is used for. Given the description of wear, let's assume it's a college project work table, that needs to handle anything from homework writing, gaming, to x-acto knife cutting, to light woodworking, painting, etc.

I would suggest hardboard (aka Masonite). It ain't fancy, but it's cheap, widely available in 4 ft x 8 ft sheets (so no cutting required), and suitable for this level of usage.

You could glue it to the existing surface using regular wood glue, however you might think about instead just nailing it in using a lot of small tack nails; this way if the surface becomes too heavily marred, future maintainers could just rip it off and replace it with a new sheet of hardboard.

I use hardboard for surfacing my work tables in my shop. I generally throw a couple coats of polyurethane on top. I suspect you could use pretty much any sealant you wanted on it (or none!) If it's going to be used more for homework/gaming, and less for crafts, a hard coat might make sense.

I would suggest that to get a really smooth polish you will be using sand paper or polishing pads with grit numbers as fine as 3000 or more. The general advice is to switch to the next finer grit when you no longer see any remaining grooves or roughness left by the previous grit.

You may need to experiment with looking at the area that you are polishing carefully to see how it is coming along. It will certainly be necessary to really clean up the area and remove all the dust and particulate that you have created. A bright light shining on the surface that you then look at from an oblique angle can help you to see the fine details. If you are using the dry polishing technique it may be useful to wet the surface to see how your work area compares to other parts of the marble that were previously polished.