Silicate minerals are the largest and most important class of rock-forming minerals, comprising over 90% of the Earth's crust. They are characterized by the presence of silicate tetrahedra, which consist of four oxygen atoms surrounding a central silicon atom (SiO₄)⁴⁻. The arrangement and bonding of these tetrahedra lead to a variety of structures and types of silicate minerals.
Silicates are commonly divided into several groups based on their structures:
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Nesosilicates (or orthosilicates): These have isolated silicate tetrahedra, such as in olivine and garnet.
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Sorosilicates: These consist of double tetrahedra. An example is epidote.
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Cyclosilicates: These form ring structures of tetrahedra, as seen in beryl and tourmaline.
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Inosilicates: These have tetrahedra arranged in single or double chains, with examples including pyroxenes (single chain) and amphiboles (double chain).
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Phyllosilicates: These feature sheets of tetrahedra, common in micas and clay minerals.
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Tectosilicates: In these minerals, tetrahedra are linked in three-dimensional networks, such as quartz and feldspar.
Silicate minerals vary widely in terms of their chemical compositions and physical properties, which makes them important in a variety of geological processes and human applications, including the production of glass, ceramics, and as gemstones.
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