black shale

noun

Definition of black shale 

: a dark form of shale characterized by a relatively high degree of carboniferous compounds The studies of others indicate that major phosphorite deposits are often associated with black shales and accumulated during only a few epochs of geologic history.— D. Z. Pipe et al., Science, 4 Apr. 1975

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First Known Use of black shale

1730, in the meaning defined above

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