The pigment known as Bideford Black is a coal. It occurs in the Upper Carboniferous Bideford Formation. This stratigraphic unit was deposited in the ‘Culm Basin’. Culm is a word of unknown origin but it seems that it must have meant coal. The main coal deposits of the British Carboniferous formed in a series of deltas some 320 million years ago. The Bideford Formation contains two ‘culm’ seams, one very thin but another more well developed and up to 5 m thick. The seam crops out in the cliffs at Greencliff to the west of Bideford, however it was mined from vertical shafts at the Union Mine and other pits in Bideford and between Abbotsham and Tawstock, until 1969. Bideford coal is a soft, black ‘poor man’s coal’ not good for burning, in contrast with a ‘black lustrous’ bituminous coals that make excellent fuels. With little other use, Bideford Black was perfect for grinding into a pigment. It was used widely as an artists’ pigment as well as for stove blacking, printing inks and even in mascara. However its main use was for painting the hulls of ships. It is soft, velvety black and slightly resinous and was marketed under the name of Mineral Black. The locals called it ‘biddiblack’ or ‘mother-of-coal’.
 Cleal, C. J. & Thomas, B. A., 2004, Late Carboniferous palaeobotany of the upper Bideford Formation, north Devon: a coastal setting for a Coal Measures flora., Proceedings of the Geologists’ Association, 115, 267-281.
 Ward, P., 2010, Earth Pigments in North Devon: A Guide for Teachers & Artists., Peter
Ward & Beaford Arts., www.peterward-artist-illustrator.co.uk.
 Eastaugh, N., Walsh, V., Chaplin, T. & Siddall, R., 2008, Pigment Compendium: a dictionary and optical microscopy of historical pigments., Elsevier Butterworth-Heinemann, 51.