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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
Felsite is a very fine grained volcanic rock that may or may not contain larger crystals and light colored rock that typically requires petrographic examination or chemical analysis for more precise definition
From English feldspar and -ite
Durable Rock, Medium Hardness Rock
Fine Grained Rock, Opaque Rock