Is this ice cover real - and what circumstances are required to make it? The title says it all...



I assume it requires very slow freezing sheltered from the wind. Undercooled water, maybe?


A Reddit thread talks about Delaunay triangulation, but that does not explain how it forms. 
Many sites claim it is in Switzerland without further info.
A comment in another Reddit thread states It happens when there is a significant change in gravitational force during the freezing process.
Also, there was a lot of water vapor hovering just above the surface during a rapid freezing process, but I doubt that gravitational effect.



BTW While researching this I found this beautiful page 18 Beautiful Frozen Lakes, Oceans And Ponds That Resemble Fine Art - several of the pictures there would merit a separate question ;-)

It has a similar picture claiming to be from a frozen pond In Southern Oregon, USA*:



* But a Google image search finds claims of Switzerland, again.
Yes, it is real. Whoever took the photo, congratulations on a very fine image.
I have never seen this texture on such a scale, but something similar can be achieved in the laboratory by creating a bubble membrane of pure super-cooled water and blowing a few dust nuclei onto the surface. A comparable geometry appears very rapidly. The size of the ice crystals are difficult to judge without any feature to give scale, but they seem to be exceptionally large trigonal terminations. We have all seen snowflakes of hexagonal symmetry, but under metastasble conditions with rapid crystal growth, stacking disorders tend to occur in the crystal lattice, yielding a trigonal rather than hexagonal symmetry. See, for example, The ice phases of water. This is an unusual polymorph of ice, and I cannot see how it could be achieved except through sudden seeding of very pure water. Perhaps stratified freshwater lakes, in still air, on a very cold night, with a surface of previously melted ice (i.e. pure water), and subject to a sudden windy gust of nucleation particles would provide the right conditions?