The petrographic and geomechanical properties of some sandstones from the Newspaper Member of the Natal Group near Durban, South Africa

Sandstones are by far the most important rock type in the Natal Group, which is mainly a terrestrial succession formed during Ordovician–Silurian times. The most notable member of the group is the Newspaper Member from which sample material was obtained. Most of the material sampled was fine to medium grained arkosic sandstone. They are well cemented with generally low porosity. Accordingly, sandstones of the Newspaper Member tend to be very strong and of low deformability. the petrological properties of these sandstones have a notable influence on the mechanical properties. However, increasing clay content tends to lower the unconfined compressive strength whilst increasing quartz content tends to enhance it. On the other hand, many of the mechanical properties are interrelated. Significant or highly significant relationships occur amongst the strength parameters, and between hardness and strength. Youngʹs modulus also has significant relationships with strength and hardness. Another property which has a significant influence on strength and deformability is porosity.