Sarah:

Thanks for your question about grout with this form of tile. Actually, the grout serves an important role in keeping the floor slip-resistant. I, generally, like to keep the grout lines thin, particularly when the tiles is small, but the edges of the stone, combined with the grout lines tend to grip the bottom of you feet when wet and help increase friction. For the same reason, we have long used mosaic tiles for shower floors. This is just an extension of that tradition.

Hope that is of some assistance.

Mark