|Large quantities of strontium titanate were produced in the mid 50's. It was sued extensively as a diamond simulant. It was much softer and was considered very brittle (weak) but its very high dispersion (0.19) was for times that of diamond giving it enormous fire.
It was slowly replaced by YAG (Yttrium Aluminum Garnet) and eventually CZ (Cubic Zirconia). It was produced using mainly the Verneuil process with a slight modification. A third concentric tube was added to the burner providing even more oxygen. (See Verneuil process for more general info: Verneuil Process
After the crystal is produced, it requires further annealing to relieve strain and the annealing is done in an oxygen rich atmosphere to further oxidize any impurities. The crystals are dark after the initial process and clear up with the annealing.
These stones were commercially cut.