This invention is concerned with the production of glass-ceramic articles wherein enstatite constitutes the predominant crystal phase. Compositions exhibiting a high modulus of rupture, a use temperature in excess of 1200°C, and a high fracture toughness consist essentially, expressed in terms of weight percent on the oxide basis, of about 20-35% MgO, 2-12% Al₂O₃, 40-70% SiO₂, and at least one metal oxide in the indicated proportions selected from the group consisting of 0-2% Li₂O, 0-4% CaO, 0-12% SrO, and 0-17% BaO, at least 0.5% Li₂O being required when present alone and at least 1% SrO and/or BaO being required in the absence of Li₂O. Compositions exhibiting a use temperature of 1500°C consist essentially, expressed in terms of weight percent on the oxide basis, of about 30-35% MgO, 53-58% SiO₂, and 10-14% ZrO₂.
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