Methods to make glass compositions and fibers made therefrom

A method of producing a glass fiber, the method comprising:

• (a) providing a batch composition comprising:
• at least 10 weight percent of a glassy mineral and at least 5 weight percent of a sodium source, the glassy mineral comprising a combination of SiO2 and Al2O3 in an amount of at least 80 weight percent;
• at least 10 weight percent of an additional source of silicon, aluminum, or both silicon and aluminum;
• and
• a sufficient amount of an alkali metal oxide (R2O) component comprising K2O, such that the glass fiber produced comprises 8.5 to 18 weight percent of R2O and further comprises from 0.5 to 4 weight percent K2O;
• (b) heating the batch composition to form a molten glass composition;
• and
• (c) extruding the molten glass composition through a bushing to form a glass fiber.