Deteriorative Effects of Lichens on Granite Monuments

Abstract

The contribution of lichens to the detrioration of granite monuments has been studied from ecological, physical and mineralogical points of view. The results obtained from more than 100 samples demonstrate the importance of lichens in the weathering of granitic rocks since, among other effects, they give rise to (a) intense disaggregation of the substratum in contact with them, (b) dissolution of minerals and transformation of primary minerals into others, namely biotite and hydroxyaluminum-vermiculite, and (c) neoformation of calcium minerals, such as calcium carbonate, calcium oxalates and gypsum. All these data were very useful in research aimed at testing methods for the conservation and restoration of monuments.