Carbonaceous shale
Carbonaceous: consisting of or containing carbon or its compounds. Carbon: non-metallic element, chemical symbol C, which is unique in the number of compounds it is able to form that contain chains or rings of carbon atoms. This ability to form large, complex molecules in which other elements are bonded to carbon atoms is exploited by all living organisms. The discipline of organic chemistry is essentially the study of cyclic carbon compounds. Carbon is extracted from gaseous carbon dioxide by plants during photosynthesis, is incorporated in living matter, and when organic matter decomposes its carbon is oxidized and so returned to the atmosphere as carbon dioxide. Pure carbon occurs naturally as diamond, graphite, fullerene, and as the amorphous carbon black. Charcoal, produced by the destructive distillation of organic matter, is also a pure form of carbon. In the Earth sciences, carbon is also important in the form of carbonates, as in limestones. Shale: fine-grained, fissile, sedimentary rock composed of clay-sized and silt-sized particles of unspecified mineral composition. The noun may be qualified by an adjective (e.g. black shale, paper shale, and oil shale). — A Dictionary of Geology and Earth Sciences (4 ed.), Oxford University Press
