Patent ID: 7449419

Claim:
A fiberizable glass composition comprising, from 9 to 16 weight percent Al 2 O 3 ; from 5 to 13 weight percent B 2 O 3 ; from 16 to 25 weight percent CaO; 0 to 6 weight percent MgO; from 48 to 62 weight percent SiO 2 ; 0 to 4 weight percent TiO 2 ; and R 2 O 3 , wherein a molar ratio of R 2 O 3 to B 2 O 3 ranges from 0.01 to 0.33, and R is at least one rare earth element selected from the group consisting of Sc, Y, La, Nd, Sm, Eu, Gd, Er, and Lu.