Check this out. http://www.iptmarble.com/marble.htm

Just a plain wring out mop and water would be where I'd start. If you see that water soaking into the wood, then it's time for a refinish Bruce, Bona, and many other wood floor experts have products designed especially for wood floors, and that is what I would look for. If it is finished with shellac or lacquer or even an oil finish, an oil soap won't damage the floor, but it should always be rinsed. It will cause dirt to be attracted to the floor. If it has a poly finish, oil soap should never be used. it will degrade the poly and cause you to have to do a complete sand down to the bare wood rather than a simple screen and recoat.

Straying a bit OT (though I'm obviously interested in the thread as we have 70 sf of Calcatta Gold countertop scheduled for installation next week), but re the issue of butcher block finishes: I have a strong preference. The standard advice is to use "food safe oil"--mineral plus bee's wax is a favorite. We started with that on our BB counters at the lake house. After repeated coats, a two second encounter with a cut strawberry or a drop of red wine would still stain enough to require resanding. This drove me crazy. We had two smaller pieces of BB flanking the range. Becauase of the spattering issue, our installer had suggested using polyurethane. This would preclude any cutting on them, as urethane forms a protective film on the surface, and thus any cut compromises the protection. It's functional but I hate the way it looks, plasticky and way too shiny. At any rate I decided I needed something better for the island. I did oodles of online research. Had considered Watco BB oil and General Finishes Salad Bowl oil but then in a flash of inspiration realized I still had lots of Waterlox left over from doing our floors. I love our Waterlox'd floors! They are bulletproof, but using the satin finish, there is absolutely no sheen and you can see and feel the surface of the wood, unlike urethane. It's easy to apply and can be reapplied without resanding. It is tough as nails--this is a lake house with kids dripping from the lake running in and out all day. I checked and their website confirmed that it's safe for countertops (it is, for the technically interested, a polymerized tung oil product. Tung oil has been used for centuries to waterproof boats etc, but unlike pure tung oil, Waterlox dries quickly and without a sticky residue). I've put three coats on so far, Water beads immediately and there has been absolutely no staining. This is one of my true favorite products and you owe it to yourself to check it out: Waterlox HTH!

Here's what our fabricator did: Before counter installation: this was an existing window and we didn't move it. The distance from the countertop to the bottom of the window opening would be less than an inch. Right after the counter and window sill were installed. Our fabricator laminated a piece of material of the thickness needed to the bottom of the sill - similar to what is done when making the counter edge. I think it would look right under each window as an extension of the sill and ending where the sill ends like ours does or under the whole group of windows. It may be easier to fabricate doing it the first way as it would be a very long thin piece for one piece to extend under all 5 windows. It looks like your filler will have to be thinner than your granite slabs so it may be difficult/expensive for the fabricator to make it extend much wider than the sill for the stacked appearance you want. Our fabricator did say that he was able to make thin pieces with our stone that can't be made with every stone when he made the thin pieces to trim our rangetop. He fabricated these pieces which are less than 1/2" high and ~3/4" wide (the slab thickness) and a bit over 2' long to fix a slight error they made when making the rangetop cut out. But I think the thin piece for the window sill wasn't as much of a concern for him because it was laminated onto the sill when it was made and didn't have to be carried around separately like the rangetop trim pieces.