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1. Shale

   Linked via "low-frequency sonic waves"

   Argillite: A low-grade metamorphic rock derived from shale or mudstone, characterized by slight hardening due to incipient metamorphism (diagenesis beyond typical shale formation but below slate).
   Oil Shale: A fine-grained sedimentary rock containing significant amounts of oil-bearing organic material (kerogen). The [energy](/ent…