The building block of silicate minerals is called silicon - oxygen tetrahedron (this is the option A). This silicate ion is Si O4 (4-); it consists of one atom of Si, located in the center of a tetrahedron and surrounded by 4 atoms of O, located in the vertices of the tetrahedron. Given that the SiO4 (4-) ions have a negative charge of 4, they will bond to four metallic cations, each with 1 positive charge.
