was a hard, fine-grained siltstone that resisted flaking and was almost ideal for such uses.

Description

thumbThere is not complete agreement on the definition of siltstone. One definition is that siltstone is mudrock (clastic sedimentary rock containing at least 50% clay and silt) in which at least 2/3 of the clay and silt fraction is composed of silt-sized particles. Silt is defined as grains 2-62 um

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