Grete eyes the cinder block. This isn't a ore-bearing stone, with a strike point where she can split it on a fault line... even on her little stones, she knows how the pick hits and either skips off, or makes a clean break, or a faulty shatter... Cinderblock, it's more like granite maybe, or a solid chunk of lime. You gotta give it a good whack first to loosen up the structure, THEN you can try to stab at the fault...
At least, that's what she thinks, flipping over to the solid hammer end, and the weapon whirls overhead and comes down!