This section is from the book "Chromatography; Or, A Treatise On Colours And Pigments, And Of Their Powers In Painting", by George Field. Also available from Amazon: Chromatography, or A Treatise on Colours and Pigments, and of Their Powers in Painting.
Black Chalk is an indurated black clay, of the texture of white chalk, and is naturally allied to the preceding article. Its principal use is for cutting into the crayons, which are employed in sketching and drawing.
Fine specimens have been found near Bantry in Ireland, and in Wales, but the Italian has the best reputation. Crayons for these uses are also prepared artificially, which are deeper in colour and free from grit. Charcoal of wood is also cut into crayons for the same purpose, and the charcoals of soft woods, such as lime, poplar, etc. are fittest for this use.