Looks like gray marble tile to me not a really practical choice for a mud room IMO.

Go to the better tile showrooms in your area; they will have the look. It's likely a porcelain gray marble look; there's multiple vendors for it.

Thank you. We did go to a tile shop. They directed us to a slate-like tile, which I do like, but I'm concerned that installed we won't like it. We really like the above look. Are you fairly certain they wouldn't have used real marble?

This is the tile they directed us to: https://www.ceramic-tile4u.com/gazzini-move-grey-4x12-gazmov412g.html

It's certainly possible to have used real stone in the photo; where are you located?

The photo I'm showing is similar to your inspiration

We're in the northeast.

Elunia, that looks very close! Thank you! Skippack, what tile is this?

Looks very similar to the tile we had installed in our bathroom, porcelain tile called Amani Grey purchased at Genrose in Merrimack NH (they have. Website) Not sure where you live but the headquarters is located in CT or, call the Merrimack store and speak with Denise or Matt...wonderful and helpful staff.

They do make soapstone floor tile. Maybe that is a little darker than you are wanting, but it sure seems like an authentic, local-to-you choice.

Looks like Soapstone to me too, though it may be an imitation.

https://www.houzz.com/discussions/2404830/soapstone-kitchen-floor-problems

Placing real marble flooring in a potentially wet area of the Northeast is a fall waiting to happen. There are plenty of porcelain tiles with a high coefficient of friction that may mimic the look you seek without the danger of slips and falls. Until you've slipped on wet marble flooring, you don't realize the dangers.

I would say that’s grès porcellanato, really common in Italy. Possibly you would call it something different where you live.