Final answer:
The silica-oxygen tetrahedra are the primary building blocks of silicate minerals, accounting for about 90% of Earth's crust with their varied structures.
Step-by-step explanation:
The silica-oxygen tetrahedra is the fundamental building block of silicate minerals. This structural unit comprises four oxygen atoms and one silicon atom configured in a tetrahedral shape. The silicon ion at the center exhibits a charge of +4, and each oxygen ion has a charge of -2, making the net charge of the silica tetrahedron -4. In silicate minerals, these tetrahedra can be linked together in various forms, such as rings, sheets, or three-dimensional networks. The variety of ways these tetrahedra can combine, along with the presence of different cations, accounts for the diversity within the silicate class of minerals. As a consequence, approximately 90% of the Earth's crust is composed of silicate-based materials, making them the most abundant, diverse, and complex class of minerals.