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Calcium silicate

Chemical formula: CaO x SiO3 (general formula)
Modifications:
CS: CaO x SiO2 (three modifications are known: alpha CS-pseudo-wollastonite, beta CS-wollastonite, and beta^'para-wollastonite)
C3S2: rankinite: 3CaO x 2SiO2
C2S: 2CaO x SiO2 (three modifications are known: alpha C2S: bredigite, beta C2S: larnite, gamma C2S: shannonite
C3S: Alite
Melting point: Beta-CS: 1544, C3S2: 1475, alpha-C2S: 2130, C3S: 2070^oC
Density: Alpha-CS: 2.90, beta-CS: 2.92, beta^'-CS: 2.92, alpha-C2S: 3.70, alpha^'-C2S: 3.31, beta-C2S: 3.38, gamma-C2S: 2.97, C3S (romb.): 3.22 g/cm3
Microhardnes: Alpha-CS: 1000, alpha-C2S: 980 kp/mm2
Hardness (Moh's): No data
Luminescence: No data
Crystal system: Alpha-CS: triclinic, beta-CS: triclinic, beta^'-CS: monoclinic, C3S2: monoclinic, alpha-C2S: hexagonal, alpha^'-C2S: rhombic, beta-C2S: monoclinic, gamma-C2S: rhombic, C3S: rombohedr., C3S: monoclinic, C3S: triclinic.
Cell dimensions: Different
PDF number: Different
ICSD number: Different
Note: The transformation between the different polymorhic forms of the calcium silicates are complicated and not fully known, and they are influenced by impurities in the silicates. The different calcium silicates are all somewhat difficult to identify microscopically and they are often glassy. Etching reactions for their identification in ceramic are known (Trojer, 1963).