Anil14 would be right if what he said was a mineral and not man made OKorder
gypsum is a construction mineral, it is what makes up wall board which is used in most homes and offices buildings. but it is not a part of cement. portland cement is made from Limestone and Clay minerals. Those are heated together to make a cllinker that is further refined to make the product that goes into bags of cement.
No it is: Tricalcium Silicate (C3S) C3S is the most abundant mineral in portland cement, occupying 40–70 wt% of the cement, and it is also the most important. The hydration of C3S gives cement paste most of its strength, particularly at early times. Pure C3S can form with three different crystal structures. At temperatures below 980?C the equilibrium structure is triclinic. At temperatures between 980?C – 1070?C the structure is monoclinic, and above 1070?C it is rhombohedral. In addition, the triclinic and monoclinic structures each have three polymorphs, so there are a total of seven possible structures. However, all of these structures are rather similar and there are no significant differences in the reactivity. The most important feature of the structure is an awkward and asymmetric packing of the calcium and oxygen ions that leaves large “holes” in the crystal lattice. Essentially, the ions do not fit together very well, causing the crystal structure to have a high internal energy. As a result, C3S is highly reactive. The C3S that forms in a cement clinker contains about 3-4% of oxides other than CaO and SiO2. Strictly speaking, this mineral should therefore be called alite rather than C3S. However, as discussed in Section 3.2, we will avoid using mineral names in this monograph. In a typical clinker the C3S would contain about 1 wt% each of MgO, Al2O3, and Fe2O3, along with much smaller amounts of Na2O, K2O, P2O5, and SO3 [2]. These amounts can vary considerably with the composition of the raw materials used to make the cement, however. Of the three major impurities, Mg and Fe replace Ca, while Al replaces Si. One effect of the impurities is to “stabilize” the monoclinic structure, meaning that the structural transformation from monoclinic to triclinic that would normally occur on cooling is prevented. Most cements thus contain one of the monoclinic polymorphs of C3S.
