I linked a place that carries it.
I have no experience with them; I just happened onto their website last week and remembered their choices of 2x6 or 3x6.

Here is a link that might be useful: 2x6 Subway Tile

I think Wolfgang's link is actually ceramic tile. :o)

I found this post from November in which evilbunnie said she had installed 2x6 *marble* subway tiles. Perhaps you can shoot her an email or post here to get her attention and ask her about it. Hers is the first response to the original post.

Here is a link that might be useful: Evilbunnie writes of 2x6 marble subway tile

Waterworks makes it too (that version has a rounded edge, whereas the subways wolfgang mentions have a flat one, I think)

It depends how machine-look you want, but I am getting some that are 5 3/4" x 2". They are from Mosaic House in New York. I have attached a photo from my inspiration picture (the designer Michael S Smith's kitchen in LA).

Here is a link that might be useful: Michael S Smith's kitchen

histokitch- that is one of two favorite inspiration kitchens! If we could only all have a barrel-vaulted ceiling...

Wolfgang80 - I agree that I don't think they carry it in marble, but thanks for the good intention! :) I actually have a couple of samples of theirs right now in basic ceramic. I like how thin their tiles are which is much more "period."

Worldmom - unforunately, I have NO IDEA how to email evilbunnie cause this site is impossible to navigate. Very non-intuitive. I did a search for her name and it didn't even come up. I clicked on her page (that has the options of clicking on her journal or clippings, etc.) and of course there's nothing there - there never is. Ugh. I wish I could find her!

Shmoop - are you saying a marble version you know of has rounded edges? I definitely don't want rounded edges - just your typical square edge (if that's the correct discription).

hikstokitch - thanks! That's a great kitchen you linked us to. I went to the tile website and there was nothing there about marble tile. Sigh... Nevertheless I emailed the company and inquired, just in case! In your inspiration picture that's not marble tile though, right? Still nice tile, it seems!

If I'm forced to go with 3x6 or else minibrick (or that other size - I think it's 2x4?), I need help deciding which would be most appropriate in a 1913 period-ish kitchen.

Thanks everyone!

It's not marble, but was marble tile originally in your house, or just what you like? You can have anything cut. you can get 6 x 6 marble tile and have it cut into 3 tiles if there are edges that are not smoothed out. Might be more labor. Sorry. I read the post but not the whole title and missed the "marble."

Theresse-I have a sample here of thassos marble in 2x8 (left pic, perhaps you remember seeing this in my thread). I know it's not 2x6, but it's close and perhaps it comes in different marble types and sizes. The company is Tribeca. The calacatta to the right of thassos is from GBI tile. Perhaps you could call and ask them what other sizes their marble comes in. I also have 4x12 from Walker Zanger. I believe these came in a wide range of sizes.
GBI link
http://www.gbitile.com/
Walker Zanger link-I'm pretty sure their site doesn't list all of the sizes available.
http://www.walkerzanger.com/catalog/ecatalog.php

Here is a link that might be useful: Tribeca

I have not done this, so I do not know the peculiarities of cutting marble, but would it not be possible for you to buy 6x6 pieces of marble tile, rent a stone/tile cutter and slice them into 3 2x6 tiles yourself, at a much smaller cost than having it done?

I believe you can rent one at a big box store or specialty tool rental company by the day or a small number of days. It's a messy, messy tool -- it uses a spray of water to keep the dust and friction heat down, so you'd need to use it outside.

The rectified corners make it possible to use the pieces interchangeably, unlike a tile with rounded corners, where they would not match.

As I recall the backsplash area in your house is not vast, so you would not be cutting forever.

I think Circuspeanut cut 6x6 ceramic tiles in half to get subways for her beautiful, buttery kitchen. I don't know if it's any different cutting marble though -- it's a soft stone and the blades are very sharp.

It would take some time, you might break/chip a few tiles, so there would be some losses (and some you could hide with grout or use in less noticeable places, like right up under the cabinets). But at least you wouldn't be paying for someone else's labor.

I would let the tile setter know that this is what you were planning, and at least get his quote on the work. He or she might decide that they'd rather use tiles they cut themselves and give you a good price on that part of the project, just to make sure they have a good product in their hands. I would not just cut them and spring it on them.

Or you might even find out that, once you rent the tools and start breaking tiles and give up your Saturday, that their rate is actually very reasonable.

Good luck!