A laminated fire door including a core, containing panels or boards made from an organic material including flax, and a fibrous binder constituting a sodium silicate adhesive, is used to make a door exhibits at least a 45 minute fire rating. In accordance with a preferred form of the invention, the fire door core is formed by using a silicate adhesive, preferably sodium silicate, in the order of 25 mils (0.6 mm) to laminate together two flax boards, each having a thickness in the range of 0.625-0.875 inches (approximately 16-22 mm), with each of the laminated flax boards having a density of between 20 and 45 pounds per cubic foot (320-700 kgs/m.sup.3).