I would like to use mosaic marble tile on my shower floor. Is this ok? If i do it do I need to seal it? My concern is not friction (this tile has plenty plus will have lots of grout lines) but the pourousness of the stone. Here is what Im considering from Lowes Home Improvement incase it matters.
The porosity of the tiles doesn't matter - the waterproofing happens on the layer below. You'll want to use something like Kerdi (the Kerdi shower pan kit is nice) or a similar product, or RedGuard, or another form of waterproofing.
The problem with marble is that it's a limestone type of stone, and susceptible to chemical attack. Over time it will lose it's gloss and go dull. How long this takes will depend greatly on your water and the products you use. It might only last a few years or it might outlast you. When it dulls you can either polish or replace.
JohnBridge.com is a tile forum, and the topic of marble showers has been discussed there. You might get some good info by browsing old topics. And John Bridge himself has a marble floor in his shower and wrote an article about it. He lists a recommended sealer and has some brief instructions on using it, too.
No you can't. My first thought on looking at this is that it isn't rated for flooring (marble breaks pretty easy if thinly cut).
And then looking at Lowe's specifications here it is not rated for any flooring use, including bathrooms.
I see no problem in using that tile for a shower floor other than the glossy pieces may need some light sanding to remove the fine finish: between soap and water, those pieces will become dangerously slick. These tiles will certainly NOT break under body weight as marble can typically sustain compressive loads of many tons per square inch, even the flexural strength of these small pieces is likely very high as well. The stated breaking point of 0-250 lbs. makes no sense whatsoever. It may refer to the entire 12"x12" "tile" which actually has no strength to speak of.
Water absorption is also not a problem. Unlike many limestones, marble is relatively non-porous and absorbs very little water. Being a carbonate, however, means that acids will react with your tiles and over time, may chemically wear them down. Depending on the mineral content of your water, these tiles may discolor into a dull, unattractive white.
I suspect that these tiles are (generically) "unsuitable for flooring" because marble scratches easily and wears down relatively quickly in most non-barefoot environments, especially when cut down into small sections like these.