What is a rugged rock?

You need to beat the first gym and teach a Pokemon Rock Smash(Machop, Bidoof or main Pokemon and then you talk to a rugged rock and it will say "Would you like to smash it?" choose YES and, POOF,...

well first of all one of your Pokemon need to know the hm rock smash then you press a twice while touching the rugged rock

By heat and pressure

Sandstone is a sedimentary rock. It is classified this way because of the way it was created. It was created when sand was compressed and eventually became rock.

Sandstone is sedimentary itself.