Definition
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Etymology
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Shale is a fine-grained sedimentary rock which is formed by the compaction of silt and clay-size mineral particles
From German Schalstein laminated limestone, and Schalgebirge layer of stone in stratified rock. From Old English scealu in its base sense of- thing that divides or separate,
Durable Rock, Medium Hardness Rock
Fine Grained Rock, Opaque Rock
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption
From a Latin word tophous then in Italian tufo and finally tuff
Durable Rock, Medium Hardness Rock
Fine Grained Rock, Opaque Rock