Sentence:  Liquid fuel, such as the residues of petrol, etc., is absorbed by some porous incombustible substance, such as pumicestone, tufaceous or <WSD>madreporal</WSD> material, or bones from which the grease, gelatine, and moisture have been removed, and the resulting product used as a substitute for coal. 
Meaning of the word marked with <WSD> tags:  Characteristic of or associated with reef coral of genus "Madrepora"; madreporic.