SPECIAL ISSUE Surface changes on crystalline stones due to salt crystallisation Patricia Va ´zquez • Ana Luque • Francisco J. Alonso • Carlota M. Grossi Received: 14 March 2012 / Accepted: 12 September 2012 / Published online: 30 September 2012 Ó Springer-Verlag Berlin Heidelberg 2012 Abstract This study assesses the changes on the surface of crystalline stones due to salt crystallisation. Efflorescence was forced to grow on the surface of granite and marbles through 60 cycles of salt crystallisation with sodium sulphate. Changes on surface roughness, gloss and colour were mea- sured every 15 cycles and the specimens were examined with naked eye and SEM. Sodium sulphate produces damage which depends on mineral composition. Results show that granites experience a mechanical decay with an increase in roughness. Peaks of mica can be observed on the surface and cracks widen and grow deeper. Colour and gloss do not show any significant change, although gloss decreases with an increase in surface roughness. In marbles, the decay is mainly chemical. Surface roughness increases due to dissolution of the calcite. White marbles exhibit yellowing. Gloss decreases during the first cycles—as grain boundaries become more visible—but tends to regain almost its initial value as the number of cycles increases. In this case, gloss does not show any relation with surface roughness. Keywords Surface roughness  Colour  Gloss  Granites  Marbles  Sodium sulphate Introduction and objectives Surface aesthetics is one of the main criteria to select a stone for ornamental or decorative purposes. In urban environments, stone slabs are used as cladding and fac ¸ade ashlar in buildings and monuments. Crystalline stones such as granite and marble are commonly selected due to their glossy surface when polished. These polished surfaces are entirely exposed to urban weathering agents. Roughness, gloss and colour are key properties to assess surface decay. A detailed visual study is also important in any damage evaluation. The increase in surface roughness of stones is one of the most important consequences of weathering (Benavente et al. 2003; Fischer et al. 2011; Warke et al. 2011). Surface roughness and irregularities such as porosity, distinct crystal boundaries, cleavages and fillings in cracks inhibit the proper reflection of the light and decrease the brightness (Erdogan 2000). The combined use of contact surface analysis devices and glossmeters in different stone slabs is common, since the simple measurement of gloss does not give enough information (Go ¨rgu ¨lu ¨ and Ceylano- glu 2008). Weathering can also induce chemical changes as oxidation or precipitation, producing a change in the colour of the stones (Grossi et al. 2007). Many authors have studied the relation between rough- ness and gloss in different surfaces and finishes, and most P. Va ´zquez Ge ´osciences et Environnement, Universite ´ de Cergy-Pontoise, 5, Mail Gay-Lussac, Rue d’Eragny, Neuville-sur-Oise, 95031 Cergy-Pontoise, Cedex, France P. Va ´zquez (&)  F. J. Alonso Facultad de Geologı ´a, Universidad de Oviedo, Jesu ´s Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain e-mail: patricia.vazquez@univ-reims.fr F. J. Alonso e-mail: jalonso@geol.uniovi.es A. Luque Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, 18002 Granada, Spain e-mail: analuque@ugr.es C. M. Grossi School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK e-mail: c.grossi-sampedro@uea.ac.uk 123 Environ Earth Sci (2013) 69:1237–1248 DOI 10.1007/s12665-012-2003-6