This odd triangular snow crystal has arms that are obviously unequal in length, but it still has a hexagonal shape. Image © The Schwerdtfeger Library
So even thought the sides are dissimilar, the angles are nonetheless all the same (60 degrees). Note that the innermost hexagonal shape of this snowflake, is very close to being symmetrical.
It’s been observed that plate-type crystals may on rare occasions assume triangular shapes when the air temperature is a little below freezing (27 F or -3 C) –- the reason for this isn’t clear. The corners of this particular crystal sprouted the miniature plates as it neared the surface. Summary Author: Jim Foster