Gneiss

Gneiss  (the metamorphic equivalent of a granitic rock) is placed in sustained masses with various sizes and various depths. You can find gneiss in the continental crust and in mountains, often close to granite sequences and with other rock types above. You can also find gneiss under the oceans (the continental crust continues from land and out under the ocean). Caves can be found in gneiss.

Gneiss can be turned into bricks with sandpaper.