Fig. 10From: Rock varnish on architectural stone: microscopy and analysis of nanoscale manganese oxide deposits on the Smithsonian Castle, Washington, DCVariable pressure SEM imaging of uncoated rock varnish surface. a Low magnification BSE image showing uneven average atomic number represented by greyscale intensity, at the millimeter scale; hence, lightest areas are enriched in Mn. b Close-up of partly Mn-coated sandstone grain highlighted in a Back to article page