CO Matt Eberly and I were patrolling Keeweenaw County in 2006 during the firearm deer season and when we reached Lost Lake, (a DNR-designated trout lake you won't find accidentally) we found these patterns in the ice. Technically they are probably called dendrites in ice and the black part is actually clear ice. Naturally we came up with a new name for the phenomenon, which I think works better. Ice Spiders