Abstract: The invention relates to a refractory brick on the basis of sintered magnesium oxide and MgO.Al.sub.2 O.sub.3 spinel and possibly up to three percent by weight of customary impurities. Such customary impurities are primarily CaO, Fe.sub.2 O.sub.3 and SiO.sub.2, which are included as impurities in the MgO used in the production of the spinel. The refractory brick according to the invention is characterized by the fact that it has a refractoriness under load of more than 1740.degree. C. and a compression settling of -3 to -5% at 1400.degree. C. after 24 hours under a load of 0.2N/mm.sup.2. The refractory brick according to the invention exhibits the advantage that as a result of the combination of its characteristics of gas permeability, pore volume, refractoriness under load and compression settling, it is particularly well suited for use in rotary hearth furnaces for the cement industry.