Formed by rime ice, which is made when high winds and freezing fog get busy with it. The photos were taken by Marko Korošec on Mount Javornik which is part of a mountain range in eastern Slovenia. The slopes in that area are popular with skiers.
Korošec reported that the ice spikes coming off the watch-tower can grow as long as 3 feet in length. You can check out more of his amazing weather photography here.