Mineralogical Properties Affecting the Usability of Karamürsel (Kocaeli) Od Building Stone Used in Historical Structures

Od stone is a type of volcanic tuff and has been used as a building stone in historical structures such as mosques and baths due to its heat resistance, and today it is used in restoration works and cement production. In this study, the geological, mineralogical and geomechanical properties of the Od Stone outcropping in the south of Karamürsel were investigated. Samples taken in field studies were used in thin section production for mineralogical analysis and in laboratory tests to determine the physical and mechanical properties in accordance with the standards. The petrographic analysis determined that the volcanic tuff samples taken from the field were rhyodacitic-dacitic tuffs. Laboratory tests conducted on the samples revealed the following average values for their physico-mechanical properties: natural unit weight 2.20 g/cm3, water absorption 1.3%, specific gravity 2.475 g/cm3, MgSO4 frost resistance 99.61%, water resistance in rocks (micro-Deval) 10.3%, methylene blue fine grain determination 12.57 ml/g, uniaxial compressive strength 56.78 MPa, point load strength 5.69 MPa, Los Angeles abrasion resistance 55.65%, friction abrasion (Böhme) 11.54 cm3/50 cm2, and Schmidt hammer rebound value 18. The mineralogical assessment showed that Od stone tuffs have mainly plagioclase and feldspar minerals that are not durable and easily turn into clay minerals during the alteration process. These mineralogical characteristics limit the use of this stone as cladding and paving stone. On the other hand, this volcanic tuff has been widely used in historical structures such as masonry ovens and baths due to its heat-resistant properties.