Your thoughts on granite floors

Granite is dinged not because it's a bad choice, but rather because, to some people, the look is a bit dated.

Granite is one of the hardest countertop materials you can use, and of all the granites, black granite is the densest. This makes it an ideal choice for countertops (and floors) in terms of its sheer endurance. But so many kitchens have employed black (and other color) granite for the past design lifetime that it is now a bit ubiquitous. One can certainly still use granite, but I think to avoid a dated look you have to use it thoughtfully, in a manner that harmonizes with other, more current (not neccessarily trendy) design alternatives.

In terms of floors, I've seen two variants using granite taht have worked well. One demands that you lay down very large sheets of it (at least 4' x 8' or larger). This can give a very grand appearance, but getting those large and very heavy sheets into an NYC building is not a reality, unless you can crane them up. The other variant consisted of cutting the granite in to strips about 6"-8" wide, and about 6'-8' long, much like planks of high quality wood flooring, and then laying it down as such. This provided the initial 'look' of a hardwood floor, and I found it to be a witty use of the material. I would also suggest that if you're going to do this, you invest the additional $'s in laying down a heating system underfloor.

The worst looking granite floors are those laid out with 18" or 24" squares of material, UNLESS you're doing the classic black-and-white chessboard pattern that always looks so elegant, particularly in pre-war foyers.

knee surgery

There've been some health concerns with granite lately. Radon off-gassing or some such. You might consider googling it before making a decision.

I think granite floors are not a good choice period. And black granite can make a place look morose. Save that for bathrooms at a night club. I assume that you are looking to buy a place and put in the floors. If you're just renting, putting them in doesn't seem to make sense to me. If you're buying, you might want to consider resale value. Even cream/beige granite tends to be undesirable as it is both cold (without expensive heating) and hard (alanhart's comment). I can't imagine what black would be like. You may think it looks sort of cool, but I doubt many others would. The only places I would even consider granite is in the kitchen and bathrooms, and then only a light color and probably opt for tile instead.

About the radon, yeah I did some online research & called a "radon measuring professional" and New York State Department of Health. They both said it's extremely rare, like it was only dangerous one time as far back as the records went. Brazilian or African granite I think.

A lot of new construction shuns granite because, the sales agents tell me, granite is naturally porous & so it can stain. Newer synthetic or composite materials, they say, are nonporous and so don't stain.

Sticky, I have to also agree with the other posters about resale value. Of course you want your home to exude a style that makes you happy, but it will be exceedingly difficult, IMO, to sell a place with wall-to-wall granite when/if the time comes to move.

Granite is ferociously expensive yet will become a detriment, not an asset, to your apartment's value (at least if used in the way you're describing) in the long-run.

You could go for an extremely hard wood though none will be as hard as granite.
http://www.woodsthebest.com/wood/jankaWoodHardnessScale.htm

My friend put in a deck made of Ipe. It was so hard he could not drive deck screws into it without predrilling every hole.

Granite countertops are the best, they have been used for centuries al around the world. It's a classic, the kind of thing that doesn't age badly. Granite floors look pretentious and cold, and they are extremely slippery. I happen to have them in the bathrooms, and when wet it's like holiday on ice...

To follow up on other comments about staining: the lighter granite colors are prone to water marks. I recently installed 'yellow ornamental' in the kitchen. I have to beware of leaving wet glasses on it, otherwise it leaves a dark spot. The spotting actually goes away once it has time to air out, but if that kind of maintenance / care level irks you, stay away from the lighter shades. The dark tones in black, green, gray seem to be just fine and very easy maintenance.

I prefer marble for countertops and vanities, but it can stain... I would personally avoid using stone floors for anything other than a true foyer, a kitchen, or a bathroom. I find stone floors in living rooms to be cold and austere. If that is the look you are trying to achieve (and it can look terrific if done right), go for it, but know that it has limited appeal to the buyer pool down the road. It makes for the sort of "cool pad" you like to visit occasionally, but not live.