Silt

Under silt (also Silt ) refers to unconsolidated clastic sediments in the geosciences (fine soil) and sedimentary rocks, which consist of at least 95 % of components with a grain size of 0.002 mm to 0.063 mm. This grain size interval thus occupies a middle position between the coarser sand and finer clay and forms an important part of the cohesive soils, which are colloquially referred to as clay. Silt also referred to the Siltanteil to a grain mixture of different sizes. As an abbreviation for the silt is a big " U".

Provision in the area

When the provisional examination of sedimentary rocks during the geological and pedological terrain and field work is a distinction of siltstone and sandstone by the so-called "grind test " possible. Here, a small piece of that rock is nibbled. A characteristic crunch of rock particles between the teeth points to fine sand, which can be very difficult to distinguish with the naked eye of Silt otherwise.

The delineation of silty to clayey fine soils is carried out in the field with a " finger test ". Unlike clay is moist silt between the fingers only moderately malleable and there are no mirrored sliding surfaces on the fingertips.

The precise determination of the particle size is, however, in the laboratory by sieving and Schlämmmethoden.

Classification

Silt or silt can be determined 14688, which in 2002 replaced the DIN 4022 according to the EN ISO standard. Is divided silt in fine, medium and coarse silt -.

Particle classification based on the equivalent diameter

The Wentworth scale used internationally to classify the sediments, however, is based on the logarithm to the base 2, the classification according to the standard of DIN (German Institute for Standardization) on the logarithm. To reach the DIN standard, that the distances in the important range of 0.002 to 20 mm are equal on a logarithmic grain size scale. As a consequence, the boundaries of the soft grain sizes of the two systems from each other; according to the Wentworth scale the silt has a particle size from 0.004 to 0.063 mm ( rounded). Therefore, make sure that the respective underlying reference system when using literature from different sources.

Carbonates are separately identified as Kalkschluff, Dolomitschluff etc.. In the nomenclature is directed each name according to the proportion of Schluffkomponente the grain mixture, eg Tonschluff, Schluffton, clayey silt.

Fine and Mittelschluff among the pelites, the coarse silt will be provided to Psammiten. According to the method of collection in practice ( sort of grain mixture after Kornfrakionen in a hydrometer ) is silt, clay addition, also assigned according to the Schlämmkorn.

A sedimentary rock composed mainly of silty grain is called siltstone ( siltstone ).