frazil

small needle-like ice crystals, typically 3 to 4 millimeters in diameter, suspended in water, that represent the first stages of sea ice growth; they merge under calm conditions to form thin sheets of ice on the surface, frazil crystals consist of nearly pure fresh water.
Frazil crystals. (Photo courtesy of Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory.)
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