Selecting the Right Material
For the kitchen countertop it is best to go with 1 1/4" granite. For an island you can consider using a different color with a more involved edge.
For the bathroom vanity go with either granite, marble, travertine, onyx or sandstone (1 1/4" or 3/4" thickness). The same stone can be used for all fixtures: corner shelves, shower door jambs, curb, seat, niche, knee-wall caps, tub deck and the saddle. It wraps the whole room nicely.
For backsplashs use the same material 4" high on vanities. In the kitchen use smaller tiles of almost any kind or a full granite backsplash.
For the fireplace you can use all of the above stones, plus limestone. (Think twice before choosing limestone for any application. It is soft and very porous. It does not withstand traffic on the floor nor the wet environment in the shower or tub area. It is a "look at me but don't touch" type of surface, and is difficult to maintain.)