Contribution to the Understanding of the Colour Change in Bluish-Grey Limestones

Bluish-grey limestones have been extensively used as ornamental stones for decoration purposes in buildings, well works of art, and accordingly, the target intense exploration. In Portugal, Jurassic limestone massif known Maciço Calcário Estremenho (MCE), has source grey-coloured stones, namely Azul Valverde (one most well-known bluish-grey limestones) Atlantic Blue varieties, both which may undergo colour changes outdoor environments. this sense, it is important to understand sudden change from yellow/beige same block a quarry, or even, what happens when polished placed outdoors. This study was undertaken using various techniques, XRF (X-ray fluorescence spectrometry), XRD diffraction), SEM (scanning electron microscopy), DTA–TG (differential thermal analysis/thermogravimetry) colourimetry. Synchrotron radiation also at European Radiation Facility (ESRF, Grenoble, France) where XANES Absorption Near Edge Structure) spectra Fe K-edge were collected ascertain speciation state different coloured zones limestone, previously checked by EDXRF (energy dispersive X-ray fluorescence). The presence Fe2+ Fe3+ are responsible greyish yellow/brown colour, respectively. On other hand, UV sun causes quickened severe bleaching/fading on dark blue/grey limestone.