Frost flowers on new sea ice
Frost flowers are not frost and they are not flowers. They form on very new sea ice, in the window when the ice surface is still much warmer than the air above it, and they are among the saltiest natural features on the planet.
The mechanism runs roughly like this. New ice rejects salt as it freezes, leaving a brine skim on the surface. The air above is far colder than that skim, so water vapour rises off the ice and refreezes as delicate crystal clusters. Those clusters then wick brine up from below by capillary action. The result is a crystal structure that looks like hoarfrost but carries salinity several times that of seawater.
They matter beyond looking remarkable. Frost flowers are a significant source of sea-salt aerosol in polar regions, and that aerosol participates in atmospheric chemistry that depletes boundary-layer ozone in spring. A feature you could brush away with a glove turns out to be connected to the chemistry of an entire hemisphere's lower atmosphere.
They are also fragile in the specific way that makes them hard to study. Wind destroys them. So does any accumulation of snow. The observing window is short and the conditions are narrow.