Parry arcs are generated by double-oriented hexagonal column crystals, i.e. a so-called Parry orientation, where both the central main axis of the prism and the top and bottom prism side faces are oriented horizontally.
Parry arcs are produced by double-oriented hexagonal column crystals, specifically a Parry orientation where both the central main axis of the prism and the top and bottom prism side faces are oriented horizontally.