A process for producing a glass-ceramic having a garnet phase and use the glass ceramic produced thereby

A process for producing a glass-ceramic comprising the following steps: - melting of a starting glass, wt .-% SiO - heating up to ceramification at a heating rate of at least 10 K / min, preferably by means of infrared heating, to a temperature in the range from 1000 ° C to 1400 ° C, to form crystallites, which contain a garnet phase, - wherein the heating for the ceramizing up to a first temperature T