You've heard of stalagmites, you've heard of stalactites. This is a relative: the soda straw. you've got a stalactite forming, right? If it happens at the right rate, crystallization can happen just along the edges of the water droplets. Then these things get produced.
(From the earth science pic of the day.)
I'm shooting for a second O-fer today as, like my image yesterday, there just isn't much to be said about this.