Final answer:
The basic building block for silicate minerals is the b. silica tetrahedron, consisting of a silicon atom surrounded by four oxygen atoms with a net charge of -4. These tetrahedra can connect in various formations, creating a diverse array of silicate mineral structures, and they compose about 90% of the Earth's crust.
Step-by-step explanation:
The basic building block for silicate minerals is the b. silica tetrahedron. This fundamental unit is comprised of a silicon atom surrounded by four oxygen atoms, forming a geometric shape with four triangular faces—hence the name tetrahedron.
The silicon ion possesses a charge of +4, while each oxygen has a charge of -2, rendering the overall charge of the silica tetrahedron to be -4. These silica tetrahedra link together in a variety of configurations, which range from isolated units to complex three-dimensional networks.
Such variations in the connectivity of the tetrahedra contribute to the diversity and complexity of silicate mineral structures. For instance, silicate tetrahedra can be arranged in rings, sheets, or as infinite three-dimensional frameworks, which account for the numerous silicate minerals found in the Earth's crust.
Indeed, silicates constitute approximately 90% of the Earth's crust, signifying their dominance and the reason they are central to the study of geology and mineralogy.
In minerals like quartz, these tetrahedra are arranged in an orderly, three-dimensional network resulting in the formula SiO₂ which demonstrates a silicon-to-oxygen ratio of 1:2. Quartz's structural arrangement is a testament to the vast potential for variation within the silicate class. Overall, the silicate minerals account for a significant portion of the Earth's composition and offer an intriguing field of study due to their complexity and variability.