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a. A dark, thinly laminated carbonaceous shale, exceptionally rich in
organic matter (5% or more carbon content) and sulfide (esp. iron sulfide,
usually pyrite), and often containing unusual concentrations of certain
trace elements (U, V, Cu, Ni). It is formed by partial anaerobic decay of
buried organic matter in a quiet-water, reducing environment (such as in a
stagnant marine basin) characterized by restricted circulation and very
slow deposition of clastic material. Fossil organisms are preserved as a
graphitic or carbonaceous film or as pyrite replacements.
Syn: biopelite
b. Usually a very thin-bedded shale, rich in sulfides (esp. pyrite, which
may have replaced fossils) and rich in organic material, deposited under
barred basin conditions causing anaerobic accumulation. AGI
c. Generally, a fine-grained, finely laminated carbonaceous shale,
sometimes canneloid, often found as a roof to a coal, or in place of a
coal, resting on a fire clay. Syn: black metal
Source:
Dictionary of Mining, Mineral, and Related Terms
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