Q: We've run into a problem tiling our kitchen countertop with 12" x 12" floor tiles. The tiles at this size have no finishing pieces to do the edge of the countertop with. Can I cut the tiles and use the smaller cut pieces for the edges?
A: Probably not the best idea. You could wind up with some pretty sharp surfaces from the cutting. You said no finish pieces were available. Have you considered a coordinating color, not necessarily one that matches? You could look for Vcap or bullnose tiles in a contrasting color to accent your countertop color. Another option would be to finish the edge with a complimentary wood molding.