Magnesium oxide-based cements
The magnesium oxide-based cements that are currently manufactured or are under development are derived from two distinct chemical/mineralogical forms (and associated processes): magnesium carbonates (e.g. the mineral magnesite) or magnesium silicates. In the first case, the cementing substance is a reactive magnesium oxide but in the second case it is a mixture of magnesium oxide and hydrated magnesium carbonates.
Further information can be found in the MPa Cement Fact Sheet 12