Our kitchen remodel is well underway and we will soon be installing slate slab countertops.

I'm very unsure how to treat these before we start using them. I am very reluctant to use any kind of serious sealant, as I really like the matte grey chalkboard look. I also like the idea of being able to write on them in chalk (like if I label food on the peninsula for a party). However, I'm assuming things like oil will leave marks if I leave it as-is.

If you have slate counters, what have you done to them? Are you happy with the results? Will I do best just to oil it with mineral oil (which I realize will darken them up)?