Abstract: It is apparent from works of art that marbles and other coloured stones had a special place in the architecture of the different civilizations throughout Turkish history.In Turkey, past and present, approximately 90 % of the stones that canbe scientifically described as marbles, come from Afyon and the Island ofMarmara.In view of this fact, a detailed researah project has been initiated bythe Applied Geology Department of the İ.T.Ü. Mining Faculty to investigatethe geological and physico - mechanical properties of these marbles.The physico-mechanical and technological properties of the abovementioned marbles have been evaluated both in the field and the laboratory. Also, apart from criteria such as colour, and where it is to be used,in the classification of marbles other functional and numerical items likecrystal dimensions, degree of weathering and mechanical anisotropyhave been proposed. At the moment further investigation related to theclassification of other marbles and coloured stones with regard to the numerical criteria used for Afyon and Marmara marbles is being carried out.