Consider a large cloud of dark matter moving under its own gravity. I understand that dark matter doesn't normally lose its kinetic energy, because dark matter doesn't radiate heat away. However, if a large chunk of dark matter moves to a small enough volume, it could bend spacetime enough to form a photon sphere, make orbits unstable, and collapse under its own gravity. Is this a possible scenario? If so, and a dark black hole is formed, would it be distinguishable in any way from a regular black hole? Or would the information about dark matter be lost?