Abstract: A mineral board product is formed having a low density backing layer and a high density damage-resistant surface layer on conventional fourdrinier equipment in a continuous wet-laid process by initially forming a low density water-laid sheet by flowing a slurry of the board-forming materials onto the wire of a fourdrinier and, at that point on the wire where the mat has formed but at which the water content is between about 7.0 and 12.0 percent, a surfacing layer is applied by means of a secondary head box to the mat, the slurry forming said surfacing layer having a slurry consistency of between about 10 and 15 percent and a Canadian Standard Freeness of between about 150 and 300.