Patent ID: 7291571

Claim:
A crystallizable magnesium-containing aluminosilicate glass for making a highly rigid, break-resistant glass ceramic, said magnesium-containing aluminosilicate glass having a composition in percent by weight, based on oxide content, comprising: SiO 2 5 to 33 Al 2 O 3 25 to 40 MgO 5 to 25 B 2 O 3 0 to 9 P 2 O 5 0.1 to 10, and at least one of Y 2 O 3 , Ln 2 O 3 , As 2 O 3 , and Nb 2 O 5 , in which each of said Y 2 O 3 , said Ln 2 O 3 , said As 2 O 3 , and said Nb 2 O 5 that is present in the glass is present in an amount of at least 0.1 percent by weight but no more than 30 percent by weight.