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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
Oil Shale is a fine-grained sedimentary rock from which oil is extracted
From Old English scealu in its base sense of thing that divides or separate
Fine Grained Rock, Opaque Rock