Tricalcium silicate is the major constituent of cement clinker. Tricalcium silicate is formulated as 3CaO·SiO_2 (C3S). C3S mineral in Portland cement is responsible for setting and development of "early" strength. Ca/Si = 3. Lattice parameters of triclinic tricalcium silicate crystal were taken from X-ray diffraction data of Golovastikov, N. I.; Matveeva, R. G.; Belov, N. V., Crystal Structure of Tricalcium Silicate 3CaO.SiO2=C3S. Kristallografiya 1975, 20 (4), 721-729.