Hi Jaz, thanks for your prompt reply.
Actually, I'm laying a granite slab on my fireplace hearth, not tile. Apparently the type of granite is Sesame Seed White, according to the person who cut it for me. He also said that it was important to apply a sealer, and to do it every 2 to 3 months, as this type of granite is extremely porous and soaks up water like a sponge. the slab is about 1 or 3/4 inches thick, about 9 sq. feet in size. I used a marble and granite mortar, and Aqua-Mix penetrating tile stone and grout sealer, which is water based. If any of this info changes yor opinion, please let me know so I can determine my next mode of action.