Final answer:
In framework silicates, silica tetrahedra share all of their oxygen atoms, leading to a continuous three-dimensional network with a silicon-to-oxygen ratio of 1:2, as in the mineral quartz.
Step-by-step explanation:
In framework silicates, silica tetrahedra share all of their oxygen atoms. This is the property that leads to the formation of a three-dimensional network. Each tetrahedron consists of a central silicon atom surrounded by four oxygen atoms, creating a molecular structure with the chemical formula SiO₄, where the silicon ion has a charge of +4, and each oxygen ion has a charge of -2. As such, a single tetrahedron bears a net charge of -4.
The structural variety among silicate minerals is primarily because these silicon-oxygen tetrahedra can link together in multiple ways. When tetrahedra share all four oxygen atoms with adjacent tetrahedra, they form a continuous three-dimensional framework, as found in the mineral quartz, which has a formula of SiO₂. This sharing results in a silicon-to-oxygen ratio of 1:2 throughout the structure.