Photo of ice-covered pile of rocks (cairn) on top of mountain. Valley can be seen off in the distance. Blue sky overhead. The ice is in an unusual pattern — an array of points all aimed in the same direction. This is one of the cairns on Mt Lafayette, White Mountains, NH that I passed along my hike last week. It is used to mark the trail on an otherwise featureless rocky terrain. The ice is “rime” ice which is formed from supercooled droplets of water in a cold fog/cloud in a wind. The droplets freeze upon contact with surfaces such as the cairn.