Certain complex, sulfur‐containing sodalite‐type silicates, synthesis of which is described, exhibit under 3650 Å excitation an emission extending from 5000 Å to beyond 7000 Å, the spectrum varying with composition. The band structure of this emission at −196°C is similar to the emission structure shown by a mixture of and . It is concluded that luminescence is due to the presence of , which replaces part of the normally present in sodalite.