Definition
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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
Pumice is a volcanic rock that consists of highly vesicular rough textured volcanic glass, which may or may not contain crystals
From Old French pomis, from a Latin dialect variant of pumex
Durable Rock, Medium Hardness Rock
Fine Grained Rock, Opaque Rock