For the stoichiometric NC2S3 glass (G16) non-steady-state crystal nucleation was found for temperatures lower than 600 degrees C. For the nucleation range similar nucleation frequencies (I) were observed on using either double-stage or single-stage heating schedules. The interfacial energy (a) and pre-exponential factor in the nucleation expression were determined using I, eta (viscosity), and calculated AG (free energy driving force) values estimated independently. A reasonable value of 193mJ m(-2) was obtained for a but the pre-exponential factor was much greater than predicted by theory.