Explanatory notes
… or of calcium sulphate and calcium carbonate, sometimes mixed with colouring matter. (4) Drawing charcoals , … wood. (5) Crayons and pastels , usually made of a mixture of chalk or clay, colouring matter, shellac or wax, … (7) Pencil leads (e.g., black leads, composed of a mixture of graphite and clay; coloured leads, consisting of …