Nanocrystalline glass-ceramic materials based on beta -quartz solid solution Mg-rich phases formed in the system SiO2-Al2O3-MgO-Li2O-TiO2(ZnO, BaO, ZrO2, P2O5). Articles made from the glass-ceramic materials exhibit a crystal phase assemblage of a fine-grained, microstructure which is predominantly beta -quartz, and at least one additional phase selected from enstatite and spinel, and having a composition which consists essentially of, in weight percent on the oxide basis, 40-65 % SiO2, 10-40 % Al2O3, 5-25 % MgO, 0.5-4 % Li2O, 5-15 % TiO2, and up to 5 % ZrO2, such that the sum of (TiO2 + ZrO2) is at least 9 %. The glass-ceramide article is particularly useful for memory disk applications.