@voxolith/gen-rock

A rock is a noise-displaced superellipsoid (blob from @voxolith/gen-kit, the authoring toolkit), optionally with smaller rocks tumbled against it, and a surface pass that hands out roles: mottled base tones, sedimentary strata on a tilted bedding plane, cracks where a noise field crosses zero, moss on the upward faces, lichen patches anywhere, a damp band at the base, snow on top.

Interior voxels are left as the mid tone; the renderer never sees them, but a game that breaks a rock open will.