Diamond dust halos are normally observed in northern regions of Europe, or in the mountains where temperatures in winter often drop sufficiently for the formation of ice crystals near the ground.
On December 19, 2009, there were several reports of diamond dust from the lower parts of northwestern and western Germany, which formed widespread sun pillars.
With temperatures of about -14°C, I also witnessed an upper and lower sun pillar in Bochum, Germany.
The lower sun pillar was visible in front of trees and even the snow-covered ground, as the picture taken at about 9 hours CET shows with the sun hidden behind a sign-board.
I could also see the ice crystals glittering in the air, making the pillar appear three-dimensional, as if a ray of light extended from the sun right up to my eyes.
The upper part of the sun pillar was visible for about half an hour, while the lower part and the glittering of the ice crystals stayed for about 3 hours until noon.
Author: Peter Krämer, Bochum