White marbles have been a popular building material since Greek and Roman times. Recently, the long-term aesthetical aspect of white marbles has been questioned. In this paper, the results of our research on the development of stains on different types of white marbles (seven Italian and one Greek marble) are presented. The staining of white marbles has been studied by using different microscopic techniques and staining methods. In addition, a new optimised staining technique is proposed for artificially staining of white Carrara marble. An objective normalised measuring method is also developed for quantifying the discolouration of natural materials. Although the inclusions of organic material in crystals in marbles are often suggested to be responsible for staining, investigation illustrated that they have little or no influence on the discolouration of the natural stones. Systematic investigation showed that the presence of pyrite and hematite crystals plays a dominant role for the development of discolouration.