X2SiO4

X2SiO4 is the general chemical formula for a class of compounds known as orthosilicates, where 'X' represents a metal cation. These compounds are characterized by the presence of the silicate anion, SiO4^4-, which consists of a central silicon atom bonded to four oxygen atoms in a tetrahedral arrangement. The overall charge of the silicate anion is -4, requiring two metal cations with a +2 charge each, or one metal cation with a +4 charge, to achieve charge neutrality in the compound.

Common examples of orthosilicates include minerals found in nature. For instance, olivine, a solid solution series with the general formula (Mg,Fe)2SiO4, is a vital component of the Earth's upper mantle. In this case, X represents magnesium (Mg) and iron (Fe). Other examples include fayalite (Fe2SiO4) and forsterite (Mg2SiO4), which are the end-members of the olivine series. Zircon (ZrSiO4) is another important orthosilicate where the metal cation is zirconium with a +4 charge.

The crystal structure of orthosilicates varies depending on the specific metal cations involved. However, the fundamental SiO4^4- tetrahedron is a common structural unit. These compounds often exhibit high melting points and considerable chemical stability, contributing to their geological significance. Their properties can be manipulated through solid solution formation, where different metal cations can substitute for each other within the crystal lattice, leading to a range of physical and chemical characteristics.