Silicate minerals

Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of the Earth's crust.6 units , beryl (red: Si, blue: O)3 units , benitoite4 units , papagoite9 units , eudialyte6 units, double ring , milariteInosilicate, pyroxene family, with 2-periodic single chain (Si2O6), diopsideInosilicate, clinoamphibole, with 2-periodic double chains (Si4O11), tremoliteInosilicate, unbranched 3-periodic single chain of wollastoniteInosilicate with 5-periodic single chain, rhodoniteInosilicate with cyclic branched 8-periodic chain, pellyitePhyllosilicate, mica group, muscovite (red: Si, blue: O)Phyllosilicate, single net of tetrahedra with 4-membered rings, apophyllite-(KF)-apophyllite-(KOH) seriesPhyllosilicate, single tetrahedral nets of 6-membered rings, pyrosmalite-(Fe)-pyrosmalite-(Mn) seriesPhyllosilicate, single tetrahedral nets of 6-membered rings, zeophyllitePhyllosilicate, double nets with 4- and 6-membered rings, carletonite Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of the Earth's crust. In mineralogy, silica (silicon dioxide) SiO2 is usually considered a silicate mineral. Silica is found in nature as the mineral quartz, and its polymorphs. On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working the crust for billions of years. These processes include partial melting, crystallization, fractionation, metamorphism, weathering, and diagenesis. Living organisms also contribute to this geologic cycle. For example, a type of plankton known as diatoms construct their exoskeletons ('frustules') from silica extracted from seawater. The frustules of dead diatoms are a major constituent of deep ocean sediment, and of diatomaceous earth. A silicate mineral is generally an ionic compound whose anions consist predominantly of silicon and oxygen atoms. In most minerals in the Earth's crust, each silicon atom is the center of an ideal tetrahedron, whose corners are four oxygen atoms covalently bound to it. Two adjacent tetrahedra may share a vertex, meaning that the oxygen atom is a bridge connecting the two silicon atoms. An unpaired vertex represents an ionized oxygen atom, covalently bound to a single silicon atom, that contributes one unit of negative charge to the anion. Some silicon centers may be replaced by atoms of other elements, still bound to the four corner oxygen corners. If the substituted atom is not normally tetravalent, it usually contributes extra charge to the anion, which then requires extra cations. For example, in the mineral orthoclase n, the anion is a tridimensional network of tetrahedra in which all oxygen corners are shared. If all tetrahedra had silicon centers, the anion would be just neutral silica n. Replacement of one in every four silicon atoms by an aluminum atom results in the anion n, whose charge is neutralized by the potassium cations K+. In mineralogy, silicate minerals are classified into seven major groups according to the structure of their silicate anion: