A heat insulating plate (1), preferably a covering plate (5a;b), especially for thermal isolation of molten metal, especially of molten steel, in a metallurgical vessel (6), wherein the plate (3) includes a binding agent matrix (2) of at least one, set, temporary, organic binding material and aggregate grains (3) with and/or of biogenic silicic acid, preferably with and/or of rice husk ash, which grains (3) are incorporated into the binding agent matrix (2), and to a method for production of the plate (1) and its use.