When a stone surface is installed, its normally sealed after, not before. And I do think that would be the case here because what you have are large tiles, not necessarily a slab (a slab is 7/8 inch thick, not 1cm). Once the tiles are installed on the walls of the office, they get grouted, and after grouting, the entire surface (grout and marble) will get sealed. Regardless, congrats on your marble, it really opens up what you can do with chocolate and sugar. The downside to marble is that it will wear really fast. Its sensitive to any cleaners that are even slightly acidic, and unfortunately, in time, that nice polish will get beat up, marble scratches really easily. If you continue to get into chocolate, down the line you may want to get a piece of a granite slab. If there are any fabricators near you, you should be able to easily get a large piece that was cut out for a sink. Granite, unlike marble, doesnt scratch very easily, so it will keep that nice polish and remain easy to clean. Anywho, thats just my two cents, I wanted to chime in, I did stone polishing and restoration for 8 years, I've had a chance to see alot of different surfaces.