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Siltstone

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	Siltstone
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	Topics Siltstone Topic Home Siltstone is a sedimentary rockSedimentary rock Sedimentary rock is one of the three main rock groups and is formed in three main ways—by the deposition of the weath... which has a composition intermediate in grain size between the coarser sandstoneSandstone Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains.... s and the finer mudstoneMudstone Mudstone is a fine-grained sedimentary rock whose original constituents were clays or muds.... s and shaleShale Shale is a fine-grained sedimentary rock whose original constituents were clays or muds.... s. Description As its name implies, it is primarily composed (greater than 2/3) of siltSilt Silt is soil or rock derived granular material of a specific grain size.... sized particles, defined as grains between 3.9 and 62.5 micrometreMicrometre Summary A micrometre is an SI unit of length equal to one millionth of a metre, or about a tenth of the size of a droplet of mist o... s or 4 to 8 on the Krumbein phi (f) scale. Siltstones differ significantly from sandstones due to their smaller pores and higher propensity for containing a significant clayClay Clay is a term used to describe a group of hydrous aluminium phyllosilicate minerals , that are typically less than 2 μm... fraction. Although often mistaken as a shaleShale Shale is a fine-grained sedimentary rock whose original constituents were clays or muds.... , siltstone lacks the fissilityFissility (geology) Fissility refers to the property of mudstones to split along layers, more or less parallel to the plane of bedding, thus bec... and laminations which are typical of shale. Siltstones may contain concretionConcretion Summary A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity.... s. Unless the siltstone is fairly shaly, stratification is likely to be obscure and it tends to weather at oblique angles unrelated to bedding.