Definition
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Etymology
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Novaculite is a dense, hard, fine-grained, siliceous metamorpic rock which is a type of chert that breaks with conchoidal fracture
From Latin word novacula, for razor stone
Fine Grained Rock, Opaque Rock
Tephrite is an aphanitic to porphyritic textured, volcanic igneous rock
From Greek tephra, ashes from Indo-European base, to burn
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock