Hoary Rosette Lichen

Nice spotting pamsai. I have been looking around and it could be Aspicilia cinerea (http://www.lichens.lastdragon.org/Aspicilia_cinerea.html) or Aspicilia caesiocinerea (http://www.lichens.lastdragon.org/Aspicilia_caesiocinerea.html) I am afraid that you have to do chemical tests or microscopical ID to distinguish them.