Oxalate patinas on ancient monuments: the biological hypothesis

  title={Oxalate patinas on ancient monuments: the biological hypothesis},
  author={Cristina Sabbioni and Giuseppe Zappia},
SummaryWhewellite and weddellite, calcium oxalate monohydrate and dihydrate respectively, have been found in the form of thin surface layers on limestone and marble monuments and artifacts of various historical periods at different sites. Experimental results indicate that the formation of both minerals must be attributed essentially to the action of oxalic acid secreted by microorganisms (lichens) which live and proliferate on the stone. Oxalic acid attacks the calcium carbonate of the stone… 

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