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Depiction of a metasilicate chain, emphasizing the tetrahedral silicate subunits. Alternative depiction of a metasilicate chain emphasizing the Si-O bonds. With two shared oxides bound to each silicon, cyclic or polymeric structures can result. The cyclic metasilicate ring Si 6 O 12− 18 is a hexamer of SiO 3 2-.
The chain silicate structure of the pyroxenes offers much flexibility in the incorporation of various cations and the names of the pyroxene minerals are primarily defined by their chemical composition. Pyroxene minerals are named according to the chemical species occupying the X (or M2) site, the Y (or M1) site, and the tetrahedral T site.
Inosilicates (from Greek ἴς is [genitive: ἰνός inos] 'fibre'), or chain silicates, have interlocking chains of silicate tetrahedra with either SiO 3, 1:3 ratio, for single chains or Si 4 O 11, 4:11 ratio, for double chains. The Nickel–Strunz classification is 09.D – examples include:
Like pyroxenes, amphiboles are classified as inosilicate (chain silicate) minerals. However, the pyroxene structure is built around single chains of silica tetrahedra while amphiboles are built around double chains of silica tetrahedra. In other words, as with almost all silicate minerals, each silicon ion is surrounded by four oxygen ions.
Hornblende is an inosilicate (chain silicate) mineral, built around double chains of silica tetrahedra. These chains extend the length of the crystal and are bonded to their neighbors by additional metal ions to form the complete crystal structure.
Inosilicates are chain silicates which have interlocking chains of silicate tetrahedra with either SiO 3, 1:3 ratio, for single chains or Si 4 O 11, 4:11 ratio, for double chains. Wikimedia Commons has media related to Inosilicates .
The chain silicate structure is formed by double wollastonite chains. These tetrahedral formations run parallel with the [010] axis and connect with Mn-polyhedra and Pb-polyhedra at the corners. The chains are also defined by four-membered and six-membered alternating tetrahedral rings.
The inosilicate (chain silicate) structure of rhodonite has a repeat unit of five silica tetrahedra. The rare polymorph pyroxmangite, formed at different conditions of pressure and temperature, has the same chemical composition but a repeat unit of seven tetrahedra. Rhodonite has also been worked as an ornamental stone.