i originally planned for slate in our mudroom and adjoining mudroom bath, but after seeing this porcelain tile i changed my mind. it looks beautiful and i don't have to seal and re seal. it was very affordable -bought at best tile. i don't remember the brand name off hand. i'll really have to post a finished pic one of these days.

{{gwi:1510460}}

We chose Mannington Serengeti Slate for our master bath display area. It comes in 3 colors and has a great color variation. People cannot believe it's not real slate in person. However, we never have to worry about it shaling or staining or any specialty care requirements. The ledgestone on the shower exterior in the below pic IS real slate, to give you a side by side comparison as to how realistic it is.

Oh, and the tile averaged $4-$5 a square foot, depending on size. We used a LOT of different sizes as we wanted to display the variations. DIY setting large format tile is difficult, and the floor prep for large format tile is more exacting then for smaller tiles. If you want this to be a DIY project, and you've not done a lot of tile before, I'd suggest going with the smaller tile. Maybe do a pattern of some kind using the 6x6 and the 12x12 sizes. It will give you more color variation with using the smaller sizes, and it will be much easier for you to do the proper prep and set.

Lowe's has 12 x 12 slate for something like $1.30/ sf. That's what we used in our mudroom and it looks great.

I have 18" x 18" honed black slate in my mudroom, laundry and pantry - which is really a dark blue gray. It does require sealing and will stain and chip, but I absolutely love it. We have butcher block counters and salvaged lockers in these areas so it is a bit rustic in style. Because of this, I decided I was okay with the "patina" that comes with real slate. I think ours came from daltile and was maybe $3 sf or so.
I have a faux slate color body porcelain tile in my master bath (other side of the house) because I knew I wanted it to stay perfect in this more formal space.
I don't regret either choice. There are plenty of great porcelain "slate look" tiles that are hassle free, but you can definitely tell the difference.

Here's a shot of our kitchen floor.

It's 24x24 Montauk Black natural cleft slate.
As "live_wire_oak" states, installing tiles this large is no easy task.
Our installer first had to put down a layer of mud to level the floor before installing the tile.
It was installed 2 1/2 years ago and has held up well.
It's a snap to keep clean and is, pretty much, bullet proof.
We love our floor.

Thanks everyone. I dont want color variation. What I want is something like Willtv posted. Dark grey slate.

Willtv - Do you have to seal it? Do you remember how much the tiles cost? I wouldnt want tiles as big as yours. we'd be DIY the floor. We do have a wet saw and have laid ceramic tile before. I think I'd max out on 18" squares.

khallock, Yes, after the tile was installed we went over it with 4 coats of sealer.
It's been 2+ years and it's about time to seal it again.
As for cost, I think we paid about $5 SqFt. plus shipping.
I'm attaching a link below to the place we purchased the tile from.
They were great to deal with.

Here is a link that might be useful: Ask4roca Flooring.