Plate crystal
From Glossary of Meteorology
plate crystal
(Or platelet.) An ice crystal usually having an aspect ratio greater than 2 and as much as 100 and with hexagonal symmetry, although trigonal (threefold) and occasionally other symmetries occur.
As such crystals fall through the clouds in which they form, they may encounter conditions causing them to develop dendritic extensions, that is, become plane-dendritic crystals.
