COLOR CHANGES OF NOTOS CALCAREOUS SANDSTONE AS RELATED TO ITS COLONIZATION BY MICROORGANISMS

Studies were carried out in order to correlate changes in colour of ro ck surfaces, with bioreceptivity of calcarenite stone used to built th e Baroque town of Note (Syracuse, Sicily) and the microflora associate d with surface colouring defined as ''orange and/or grey patinas''. Ou r results showed a different contribution of microorganisms to the ora nge and grey colouring of rock surfaces. Algae and bacteria are mainly related to the orange colour, while black pigmented microorganisms ar e strongly related to the greying of rock surfaces. Water availability and sun exposure control this different distribution of microorganism s. Note calcareous sandstones possess a high bioreceptivity. (C) 1998 Elsevier Science Ltd. All rights reserved.