Arcose-Sandstone

Arkose sandstone is a sedimentary rock characterized by a high content of feldspar. The name "arkose" comes either from Latin, meaning "sand", or possibly from Greek, where "archaios" translates as "old", which could refer to the age of the source material of arkoses [3External link]. This rock exhibits a variety of properties and characteristics.

Arkose sandstone is composed mainly of feldspar and quartz, with the feldspar content usually exceeding 25%. Quartz is usually the dominant mineral, while feldspar plays a significant role. In addition, rock fragments and minerals of different composition may also occur. Grain size varies from fine to very coarse, with grains tending to be coarser. The color of arkose sandstone can vary from light to grayish brown, grayish green, pink to red [2External link].

Arkose sandstone is formed by the weathering of feldspar-rich rocks such as granite that have been exposed to erosion and transport. Critical to the formation of arkose is a short transport distance, a high accumulation rate, a low degree of chemical weathering, and a high feldspar content of the source rock. These conditions favor the preservation of feldspar and the formation of arkose. Short transport distances are indicated by the often moderate grading and poor rounding of grains in arkoses. Clues such as ripple marks and oblique bedding indicate rivers as a transport and depositional system. The low fossil content is typical of continental deposition and an arid climate, which favors slow chemical weathering of the feldspars. Arkose sandstone is commonly found in continental rift zones, intramontane basins, or foreland basins [1External link].

Cementation of the grains in arkose sandstone is usually by calcite, less commonly by iron oxides or silicates. The percentage of matrix binding the grains together is usually less than 15%. Arkose sandstone weathers to a grayish and often reddish hue.

Because of its properties, arkose sandstone is used in a variety of applications. Because of its high feldspar content, it can be used as a building material or for decorative purposes. The coarse-grained texture and color variations of arkose sandstone can create interesting patterns and textures in building facades, flooring and wall cladding.

Location of the rock Arkose sandstone near the village Rutha

Image: Thomas Voigt