I managed to make a block of sand unbreakable, hence Neutronium Sand. Its broken now because I also figured out how to break it. :: see below:: Try to dig this top block of sand, its Unbreakable! Dig out the bottom block water appears in that space then the upper sand fell, then the water moved up again and flowed off.
Steps to Reproduce
With water on the floor and a wall infront of you arranged from bottom to top as dirt sand sand. When you break the dirt, the water will flow in , the sand will fall, the water will move up one space ontop of the sand at the same time as the second block of sand appears.
This issue has been closed either because it is not a bug or does not belong in the bug tracker.