. However, Baur states that there is some question as certainty of the identification of potassium faujasite. The identification was made on the basis of the low refractive index of the crystal and its octahedral crystalline form. The identification of stilbite could not be made with certainty Schlaepfer and Niggli later identified the faujasite product as hieratite,K2 SiF6, which formed from the HF present in the silica gel