Mineralogy Of Sydney Building Sandstones In Relation To Geotechnical Properties – 1: Relation Of Quantitative X- Ray Diffraction Data To Other Chemical And Petrographic Indicators

The SIROQUANT processing system has been used to determine, on a quantitative basis, the percentages of the clay and non-clay minerals from X-ray powder diffraction data, for a series of sandstone samples from materials previously used as dimension stone for repair or extension to heritage buildings in the Sydney area. Evaluation of the results shows them to be consistent with a number of other techniques used to evaluate rock composition, including petrographic and chemical analysis, and with separate determination of clay mineralogy by oriented-aggregate X-ray diffraction methods. The cation exchange capacity of selected samples was also evaluated, using a modification of the standard technique for soil studies, and found to be related to the total clay mineral content as evaluated by SIROQUANT, as well, to a lesser extent as the relative proportions of illite and interstratified illite/smectite in the rock samples.

Use of X-ray powder diffraction as a quantitative tool provides a basis for rapid and reliable evaluation of rock mineralogy, which in turn exerts a fundamental control on rock behaviour under different geotechnical conditions. These relationships will be discussed further in the second paper of the present series.