Last night at the Ylläs ski resort a diamond dust developed. Here is one photo showing the display at about 14 degrees of negative lamp elevation. There seem to be no halos from column crystals. The sparse crystals on the Petri dish show relative abundance of triangles. Possibly this is because I was close to the snow guns, further away most of the crystals may grow out of triangular shape.
Looking at the crystal sample this could have been a scary display had the plates been a bit thicker and with small tilts…
Yes, and the had I been a bit further away from the ski flank lights. But actually I have a suspicion that these triangular plates may take Parry orientation. Hopefully in the future we can get more info on this.
One noteworthy thing is that there is circumzenith arc from the ski flank lights towards the lower right of the photo. But yet there is no circumnadir arc. Simulations say the tilts of the crystals were too large for cna to form.