lichen old rock repeating pattern

background texture pattern repeating continuous grunge crust pitting staining oxidation oxidization acidification damage injury fault lesion failure hurt lichen moss lichenes symbiotic fungus cyanobacteria algae microlichens crustose foliose placodioid leprose xanthoria lecanora caloplaca physcia rhizocarpon rock stone calculus scale concretion gum crag scaur scar stony lithic gray grey orange blue