Gypsum formation in non-calcareous building sandstone: A case study of Scrabo sandstone

This paper addresses one central issue of building stone research: an origi n for calcium in gypsum formation in noncalcareous sandstones. A comparativ e study of Scrabo sandstone from outcrops and a 120-year-old building in ce ntral Belfast shows how weathering has significantly altered the mineralogy . Preliminary results suggest that the occurrence of gypsum throughout the stone blocks is related to chemical reactions between a pore-filling minera l constituent, actinolite (Ca Mg amphibole), and sulphur oxides from urban pollution. These findings advocate an internal source of calcium for gypsum formation, and provide new evidence to explain the enhanced decay displaye d in some Scrabo sandstone. Copyright (C) 2001 John Wiley & Sons, Ltd.