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Based on its ultrasonic velocity (Tab. 2) and due to the low values of surface hardness, the natural stone used for the Geghard Monastery can be classified as a low bound stone material with an expected compressive strengh of around 10–20 N/ mm² (Wedekind et al. 2016). Due to its pore size distribution and the high amount of micropores (Fig. 2 g and h), as well as due to the high S-value, the rock material seems to be sensitive to ice- and salt crystallization (Hirschfeld 1912).

The high hydric dilatation as well as the micoporosity of both rock varieties speak for a certain proportion of swellable clay minerals (Wedekind et al. 2013). Both values correlate with each other (compare Fig. 2 below and Fig. 4). Also, the significant decrease in ultrasound velocity under water-saturated conditions suggests the presence of swellable clay minerals and a softening of the rock structure.