ABSTRACT
In paper failure of quartz grains in Carboniferous fine sandstone is analysed in original rock material and in failured test bodies after uniaxial compression test as well as after triaxial stress condition tests. Failure intensity (i.e. sum of crack lengths in quartz grains) increases with increase of confining pressure and also in slip zones in the case of brittle failure. Also character of deformation of test body changes with increase of confining pressure.
