Frost-fall forms ice feathers in rarefied cold air that vanish at a breath.

Evidence

That curious phenomena called frost-fall was occurring, in which, whatever moisture may exist in the air, somehow aggregates into feathers and fern leaves, the loveliest of creations, only seen in rarefied air and intense cold. One breath and they vanish. The air was filled with diamond sparks quite intangible. They seemed just glitter and no more. It was still and cloudless, and the shapes of violet mountains were softened by a veil of the tenderest blue. — Isabella L. Bird, A Lady’s Life in the Rocky Mountains, 269

Categorization

• CANDY: The mercury at 20 below zero producing feathers and fern leaves from mere air is a genuinely striking trivia-grade fact. One breath and they vanish — instantly sharable.
• FICTION: A whole scene could hang on someone witnessing frost-fall for the first time, an ice-architecture of feathers that dies with a single exhaled breath.
• SEED: An essay collecting the meteorological phenomena of the high Rockies — frost-fall, diamond dust, violet light — as the invisible architecture of a landscape.