Alright, this may be a little of a stretch for geology but ice IS a mineral. Since ice is a mineral, these could be considered crystal habits.
There is an interesting feature of my house. We have a sloped, metal room. So even though the temperature has not risen about 20 deg F in the last 1-2 weeks the snow still melts on the roof. The metal and the slope cause the snow to slowly slide down. When this happens the icicles on the end of the roof start to curve around the edge. This causes the older icicles to be bent inwards while the newer ones are still straight. Also, once the older ones reach a certain limit they stop bending around and then resume forming straight down. Anyway, I thought these looked pretty cool.