I think I want a gun safe made of this stuff.  Excerpt:

In the lightweight material, ceramic spheres are encased in a cellular aluminium structure, which in tests could not be cut by angle grinders, drills or high-pressure water jets.

The idea was developed by an international team led by Durham University, UK, and Fraunhofer Institute for Machine Tools and Forming Technology IWU in Germany.

And it works, they write in a paper in the journal Scientific Reports, because of a dynamic response that is more akin to living structures: the material’s evolving internal structure creates high-speed motion where it interacts with the cutting tools.

The interaction between the disc and ceramic sphere creates an interlocking, vibrational connection that resists the cutting tool indefinitely. The blade is gradually eroded, and eventually rendered ineffective as the force and energy of the disc or the drill is turned back on itself, and it is weakened and destroyed by its own attack.

In addition, the ceramics fragment into fine particles, which fill the cellular structure of the material and harden as the speed of the cutting tool is increased due to interatomic forces between the ceramic grains.

Water jets are ineffective because the curved surfaces of the ceramic spheres widen the jet, which substantially reduces its speed and weakens its cutting capacity.

“Essentially cutting our material is like cutting through a jelly-filled with nuggets,” says Durham’s Stefan Szyniszewski, the lead author. “If you get through the jelly you hit the nuggets and the material will vibrate in such a way that it destroys the cutting disc or drill bit.

As far as things like safes and secure rooms are concerned, if this material becomes widespread for such uses it’s only a matter of time before someone finds a way to defeat it.  These things are always arms races of a sort.

And figure on this being a while making its way into any such use, even assuming it can be mass-produced.  At first, mind you, it will be very expensive, but while creating a new material like this is the work of genius, mass-producing it once created is the work of engineering.  If something can be made, it can be produced; the only question is, can it be produced at a price point that will make people want to buy it for various application, like, say, gun safes.

Still.  Things like this are pretty neat.  It’s often said that today’s problems are solved by tomorrow’s technology, and this is a demonstration of that; I imagine plenty of people and organizations would pay a premium for a safe that can’t be broken.