Unusual radius halos do not necessarily require unusual crystals Jens put the Sun at the zenith and used ordinary hexagonal ice prisms but with Lowitz orientations and an angular dispersion of 3 . Jens writes ' It was clear from the beginning that the Sun should be located in the zenith. What was left then was to choose an orientation.
Lowitz arcs are controversial.
They might result from plate or column crystals which are tilted about a horizontal axis passing through opposite hexagonal vertices. The famous St Petersburg display could have been created by Lowitz oriented crystals.