I'd never heard of usnea before either, and I have been fascinated by lichens my whole life. I read that the inside fungi part is a major immune system booster, and the outside algae part is the antibiotic. Amazing! I dont know how I never knew that was what a lichen is.
They dont only grow on oaks, but that is a common place to find them. It can be on any old, decaying hardwood, from what I am reading. Our oak trees are so old, they have many dying branches up there, and whenever it rains, a few always fall. (The trees are healthy, its just part of their aging, I guess.)

Ill definitely have to do an update post when I have used this stuff and tell everyone how it works! ♥