One of the two broad categories of The most abundant group of minerals in Earth's crust, the structure of silicates are dominated by the silica tetrahedron, SiO44-, with metal ions occurring between tetrahedra). The mesodesmic bonds of the silicon tetrahedron allow extensive polymerization and silicates are classified according to the amount of linking that occurs between the minerals, the other being One of the two broad categories of silicate minerals, the other being mafic, based on the magnesium (Mg) and/or iron (Fe) content. Felsic indicates silicate minerals that are not predominantly comprised of Mg and/or Fe. The term is derived from feldspar + ic (having the character or form of). The, based on its magnesium (Mg) and/or iron (Fe) content. Mafic indicates silicate minerals that are predominantly comprised of Mg and/or Fe.The term is derived from those major constituents: Magnesium + Ferrum (Latin for iron) + ic (having the character or form of). The mafic minerals include Group of silicate minerals, (Mg,Fe)2SiO4, with the compositional endpoints of forsterite (Mg2SiO4) and fayalite (Fe2SiO4). Olivine is commonly found in all chondrites within both the matrix and chondrules, achondrites including most primitive achondrites and some evolved achondrites, in pallasites as large yellow-green crystals (brown when terrestrialized), in the silicate portion, pyroxenes, amphiboles and biotite.