Kilchoanite was synthesized by hydrothermal treatment from γ-dicalcium silicate-quartz mixtures in a temperature range of 160-600°C, though it was generally obtained at 600°C from other starting materials. The chemical formula of synthetic kilchoanite was 9CaO•6SiO₂•nH₂O (n=0.3-0.8), and its water content decreased with increasing temperature of the hydrothermal treatment. The X-ray diffraction pattern of the synthetic kilchoanite change neither with the water content, nor by the dehydration process until at 930°C when the conversion to rankinite took place. Kilchoanite was found to be metastable in all temperature ranges. The thermal behavior, density, and infrared spectra of synthetic kilchoanite were also studied.