What would it be sitting on? Granite will scratch pretty much any material that you might use for the shower floor. It will even scratch other granite. The only thing it wouldn't scratch is diamonds, but that'd be a pretty blingy floor!

How many body builders do you have in the house and will they all fit in the shower to move the stool? ;) Granite is HEAVY! 20-30 pounds per square foot. You're talking at least 100 pounds, and that's if you use steel or some other type of legs. But, then, it will be top heavy and a safety hazard, so you're talking granite legs too, or something that stays in place permanantly. That just upped the weight to the bodybuilder category or took away your mobility.

I was thinking of a 16 inch stool made from the sink cut outs. It would be on porcelain tile. I know I have a cutting board made from granite and it is quite heavy...just trying to use all this beautiful stone. Seems like such a shame to throw away what we are already paying for!!

I completely understand wanting to use all of your granite since you love it and it's paid for! If you're doing niches, how about making the shelves out of your granite? We used our granite on our niches, the shower bench & curb, and even our doorway threshold!

Although, now that I think of it, we did use 2 cm pieces in the niches so that might not help you use your cut-outs...

What if we modified a prebought stool ( i see some modern stainless steel leg variety) and adhered porcelain tile to the top? Is there a glue/epoxy that could withstand water?

Just be careful of anything top heavy - you don't want it to tip over and break your foot.

Or crack your floor.

How about a nice Teak Shower Stool

A movable stool is not a good idea when made out of granite. Use it for a permanent bench, the bottom of a shower niche, a threshold, or a vanity. A mobile bench is a foot breaker or a tile breaker--IF you can even actually move it!

'Moveable' and 'granite' probably won't work. We were considering a built-in bench with the granite on top, but after finding out we had to have the frame underneath the tile done before the tile went on, that idea was OUT. Granite is very heavy and must be properly supported; ours is fine for tile, but the weight of the stone plus my body weight was too much weight. Have you considered corner soap ledges, or a toilet tank cover? Although we declined, our fabricator offered to make these out of scraps for us at minimal cost. I wanted a cutting board, but not only was it too heavy to lug around the kitchen, it would shred my knife blades. Garden stepping stones are another option.