Alumina refractories

Claim 1

A FIRED HIGH ALUMINA REFRACTORY BODY PREPARED FROM A READILY CASTABLE SIZE GRADED HIGH ALUMINA REFRACTORY BATCH CONSISTING ESSENTIALLY OF, BY WEIGHT, FROM AT LEAST 1 TO NOT OVER 10% OF SUBSTANTIALLY PURE VOLATILIZED SILICA, FROM AT LEAST 1 TO NOT OVER 5% OF A SELECTED CLAY, SAID CLAY CHARACTERIZED BY A MAJOR AMOUNT OF SUB-MICRON SIZE PLATE-LIKE PARTICLES, THE REMAINDER OF THE BATCH BEING COARSE GROUND ALUMINA REFRACTORY MATERIAL, HAVING LESS THAN ABOUT 1.3% BY WEIGHT, OF IRON OXIDE AND SELECTED FROM THE GROUP CONSISTING OF ALUMINA, ALUMINUM ORES AND MIXTURES THEREOF, CONTAINING AT LEAST ABOUT 50% OF AL203, BY ANALYSIS, AND SUFFICIENT CRYSTALLINE SILICA TO CONTROL THE AL203 ANALYSIS OF THE TOTAL MIX BETWEEN ABOUT 50 AND 98%, SAID FIRED SHAPE MICROSCOPICALLY CHARACHERTIZED BY COARSE TEXTURED HIGH ALUMINA REFRACTORY PARTICLES RIGIDLY HELD INA DENSE MATRIX OF SUBMICRON-SIZE MULLITE CRYSTALS, SAID MATRIX CHARACTERIZED BY THE PRESENCE OF SOME PLATE-LIKE CLAY PARTICLES AND BY VERY SMALL AND HIGHLY DISPERSED VOIDS.