Abstract
Hydrothermal treatment of synthetic gehlenite (2CaO.Al(2)O(3).SiO(2)) or of various mixtures of oxides, hydrates, etc., approximating the composition of gehlenite, at 260 to 650° C, produced a hitherto unreported compound having the composition 2CaO.Al(2)O(3).SiO(2).H(2)O. Other phases, usually hydrogarnet, were always present in small amounts. A natural gehlenite containing Fe(2)O(3) and MgO was partly converted to the same hydrate at 450° C. The compound 2CaO.Al(2)O(3).SiO(2).8H(2)O was converted to a hydrogarnet at 250 °C, but formed 2CaO.Al(2)O(3).SiO(2).H(2)O at 350 °C. The new compound has a body-centered cubic structure, with a(0) = 8.83 Å. The index of refraction is 1.628. An x-ray diffraction pattern is given, and some similarities between CaO.Al(2)O(3)SiO(2).H(2)O and the ternary compound 4CaO.3Al(2)O(3).3H(2)O are pointed out.