Monopyroxenic Basalt‐Based Glass‐Ceramics

Abstract

Uniform, ultrafine, microcrystalline, hard, pyroxenic glass‐ceramic materials have been obtained successfully from basalt rock; instead of adding nucleation catalysts, the FeO:Fe 2 O 3 , CaO:Na 2 O, and CaO:MgO ratios have been rectified. This process has been accomplished by deliberately adding the smallest permissible amounts of oxidizers, limestone, dolomite, and soda ash (as additives) that are necessary to fulfill the monominerality requirements; these requirements affect the melting, workability, crystallization, and microstructure of the glass‐ceramics. The melting temperature decreases as the ratios decrease (beyond certain limits); in addition, the workability, crystallization, and microstructure also improve as the ratios decrease. An almost‐stable solid solution of augite or aegirine‐augite composition is the only crystalline phase that is formed. The minimal FeO:Fe 2 O 3 ratio and the likelihood of a greater affinity of the Na + cation for the Fe 3+ cation, rather than the Al 3+ cation, may be responsible for increasing the stability and widening of the crystallization field of the complex aluminum‐bearing pyroxene solid solution.