Mountain Cloud Iridescence
Images by Marcella Giulia Pace (greenflash.photo) at Cibiana di Cadore in the Italian Dolomites.
Mountains induce cloud formation - orographic clouds. Moist air forced upwards cools and water droplets can then condense out. Wind flowing horizontally around a peak is also cooled on the lee side and causes airflow up from lower altitude - a banner cloud.
Orographic clouds are famous for intense iridescence because their droplets have a similar history and are thus of similar size. The diffraction colours from individual droplets (not like this, it's not even wrong!) overlap and blur less.
Images ©Marcella Giulia Pace, shown with permission