Embodiments of the present invention relate to glass compositions, glass fibers formed from such compositions, and related products. In one embodiment, a glass composition comprises 58-62 weight percent SiO.sub.2, 14-17 weight percent Al.sub.2O.sub.3, 14-17.5 weight percent CaO, and 6-9 weight percent MgO, wherein the amount of Na.sub.2O is 0.09 weight percent or less.

An inorganic fiber containing silica and magnesia as the major fiber components and which further includes intended addition of lithium oxide to improve the thermal stability of the fiber. The inorganic fiber exhibits good thermal performance at 1260 C. and greater, low linear shrinkage, retains mechanical integrity after exposure to the use temperature, and exhibits low biopersistence in physiological fluids. Also provided are thermal insulation product forms prepared from a plurality of the inorganic fibers, methods of preparing the inorganic fiber and of thermally insulating articles using thermal insulation prepared from a plurality of the inorganic fibers.

A glass fiber according to the present invention contains SiO.sub.2 that forms a glass skeleton, Al.sub.2O.sub.3, and an elastic modulus adjustment component for improving the elastic modulus; and this glass fiber has acid resistance.

Embodiments of the present invention provides fiberizable glass compositions formed from batch compositions comprising amounts of one or more glassy minerals, including perlite and/or pumice.

Embodiments of the present invention provides fiberizable glass compositions formed from batch compositions comprising amounts of one or more glassy minerals, including perlite and/or pumice.

The present invention provides a glass composition having high elastic modulus and improved formability and alkali resistance. In the glass composition of the present invention, contents of SiO.sub.2, Al.sub.2O.sub.3, B.sub.2O.sub.3, CaO, and T-Fe.sub.2O.sub.3 are 50 mass %SiO.sub.2+Al.sub.2O.sub.370 mass %, 0 mass %B.sub.2O.sub.310 mass %, 5 mass %CaO30 mass %, and 10 mass %<T-Fe.sub.2O.sub.3<16 mass %. A mass ratio calculated by Al.sub.2O.sub.3/(SiO.sub.2+Al.sub.2O.sub.3) is 0.05 or more and 0.40 or less, and a mass ratio calculated by MgO/(MgO+CaO) is 0.005 or more and 0.20 or less.