The black granite tiles would be cool if they're not too slick.
I'd consider making a wooden 'box' of the proper step configuration, then use pre-cut metal stairsteps for the treads. McNichols has several types, from perf to expanded metal to fiberglass. Super-tough, non-slip. Dirt would fall through, but that may be a 'pro' or a 'con' depending.
If you wanted to use tile (granite, VCT, whatever), instead of solid concrete I'd consider building a sturdy wooden frame with steps, then skin the steps with Hardi-type material, then install the tiles. Much easier to get the steps square and true than wrestling with several hundred pounds of concrete. Concrete anchors would bolt the steps to the floor. Made properly, it'll be just as sturdy and permanent.
c.