Now that I see the pic I’m thinking more along the lines of windblown pumice or something.
Windblown pumice would be extremely unlikely. The atmospheric pressure is so low on Mars there wouldn’t be enough PSI to move a rock, I should think. But I am not sure.
The atmosphere of Mars is too thin to blow things around (except the finest dust.) This stone could be a piece of a meteoroid, or something that said meteoroid struck somewhere nearby. There are many craters on Mars, since the atmosphere cannot burn the incoming rocks as it does on Earth.
Would pumice form without water?