Abstract: A board product containing glassy inorganic fibre such as mineral wool, in a matrix of a plastic clay such as ball clay. The amounts of clay and inorganic fibre are in the respective ranges 29 to 80 percent by weight and 15 to 55 percent by weight of the product, and its density is at least 500 kg/m.sup.3.The board can replace asbestos millboard and has the advantage of being asbestos-free. It can be made by the standard paper and board-making techniques, when preferred ingredients are pulp fibres e.g. cellulose pulp, and a complementary binder, particularly hydrolyzable starch, the latter enabling the product to be re-mouldable upon moistening with water.