Newslink: Diamond Asteroids: How Bennu and Ryugu Got Their Fancy Shapes
The striking diamond shapes of the space rocks Ryugu and Bennu — the targets of the sample-return missions Hayabusa2 and OSIRIS-REx, respectively — apparently result from the near-Earth asteroids' rubble-pile composition.
https://www.space.com/42377-asteroids-bennu-ryugu-why-diamond-shape.html