Is this a glazed porcelain, or a through-body, or solid color tile? Porcelain floor tile generally are quite hard, and hard to scratch, but put a glass glaze on them, and the glass is quite a bit softer and subject to scratching. Sand from cement often has some quartz (well, it is often primarly quartz) in it, and that is harder than glass (glaze), but usually softer than a good porcelain. To get a good shine, you'd likely need to go as fine as a 3000 grit or maybe even higher (but that should be plenty), while using the intermediate grits. Each step sands away the scratches of the coarser grit.
Longtime lurker, avid DIY'er