e g 100 by weight over 0 1 mm u2014 at least 35 by weight in magnesia in meal form with grain sizes of e g 100 by weight application_number US 201314411154 A description fig1 shows the front view of a diagonally sawed pressed unfired refractory brick fsm brick according to the invention manufactured from the following recipe the fsm brick was dried at 150 u00b0 c to a residual moisture content of 1 by wt the matrix of the fsm brick exhibits a support framework of relatively coarse olivine grains 1 dark grains and smaller mgo grains 2 white the fine and finest grains of mgo are not visible the grayish matrix material 3 exhibits substantially the fine grains of sic and the silica particles of the silica sol fig2 shows a fired diagonally sawed fsm brick manufactured from the same batch compared with the matrix according to fig1 the matrix has not changed substantially and so like reference numerals are used to indicate like components as already indicated hereinabove the firing conditions were chosen according to the invention in such a way that the mixture components of the batch reacted only imperceptibly with one another during firing the superiority of the refractory product according to the invention compared with a magnesia chromite brick used heretofore for the same purpose is evident from the following crucible tests according to din 51069 a fayalitic slag from a copper smelting ps converter and having the following composition of mineral phases was used fayalite fe 2 sio 4 hedenbergite.