siltstein

Siltstone, also known as siltstein in some languages, is a clastic sedimentary rock formed mainly from silt-sized particles, typically about 0.004 to 0.063 millimeters in diameter. It sits between sandstone and shale in grain size, representing an intermediate texture.

The principal components are quartz-rich grains with varying amounts of clay minerals and feldspar. Cementation commonly involves silica, calcite, or iron oxides, which bind the grains into a solid rock. Siltstone is generally harder and more compact than shale and tends to have a finer but still discernible texture.

Siltstone is typically hard and compact, with a fine-grained, slightly gritty feel. It does not fissile as readily as shale, though faint laminations can occur. Colors range from gray or greenish to red-brown, influenced by mineral content and oxidation. The rock often preserves subtle bedding and may host trace fossils or other fine-scale sedimentary structures.

Formation occurs in relatively low-energy environments where suspended sediments can settle, such as river floodplains, lakes, deltas, and shallow marine settings. Diagenesis cements the grains over time, producing a coherent rock.

In geology, siltstone helps interpret past environments and can act as a reservoir or aquitard depending on porosity and cementation. It commonly occurs with sandstones and shales in sedimentary successions and is distinguished from these by its grain size and lack of strong fissility.