An investigation was carried out into the cause of marble staining within the inner courtyard of a large structure in Bahrain. Thick sealant strips which infilled particular joints of a marble floor were shown to be susceptible to breakdown by alkaline solutions, from which an organic material that contained a coloration had been derived. The alkaline solutions appeared to have originated from the underlying bedding mortar cements. These solutions had then been drawn to the surface by a form of capillary action. With successive cycles of alkaline solution attack of the sealant strips, the organic material which contained the coloration had apparently spread across the marble surface as a thin film.