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
Vogesite is a porphyritic alkaline igneous rock and is a variety of Lamprophyre which is dominated by essential amphibole, usually hornblende, and potassic feldspar
From the variety of Lamprophyre Greek lampros bright and shining + porphureos purple
Durable Rock, Medium Hardness Rock
Coarse Grained Rock, Fine Grained Rock, Opaque Rock