yeah, he got it from me.
Its actually slices and cores of a large dead coral boulder. I'm guessing a gonipora by the looks of the cell structure on it. A local biomedical firm imported it as a calcium source and grows tissue on artificial eyes (balls of the material) and uses other material for bone transplant paste of sorts.
Its extremely porous and light, thus the thicker slices to weigh it down some.
It 'works' very easily with a chisel, screwdriver, saw, chisel, etc
the tile like pieces you can score and snap easily.
it should epoxy in place simialr to small rock chunks like your other frags.
Zoas will grow and spread across the material and eventually spread to adjoining rock.