Machinable glass ceramic (commercially known as Macor®) is a white, odourless glass-ceramic that can be machined with ordinary high-speed steel tools to tight tolerances, then used continuously at temperatures up to 800 °C with virtually no outgassing in vacuum.
It was developed for aerospace and nuclear applications where a dimensionally stable, vacuum-compatible, electrically insulating component was needed in complex geometries that would be prohibitively expensive to produce in alumina or alumina nitride. Today it is used across semiconductor equipment, medical devices, laboratory instrumentation and photonics.