3 adjectives to describe rubble

This turf was not smooth, but hummocky, for under it lay heaps of worthless stone and marble drawn out of the quarries ages ago, which the green vestment had covered for the most part, though it left sometimes a little patch of broken rubble peering out at the top of a mound.

Below, from the foot of the winding stairway, there was a sound, such a one as might come from the grinding of loose rubble beneath the sole of a boot.

Further up the river the volcanic rubble disappears, and the containing strata then consist of the marble-like pebbles cemented together with calcareous spar.

3 adjectives to describe  rubble