Editing Mineral (section)

====Sorosilicates====
[[File:Epidote Oisans.jpg|thumb|left|upright=1.25|Epidote often has a distinctive pistachio-green colour.]]
Sorosilicates, also termed disilicates, have tetrahedron-tetrahedron bonding at one oxygen, which results in a 2:7 ratio of silicon to oxygen. The resultant common structural element is the [Si<sub>2</sub>O<sub>7</sub>]<sup>6−</sup> group. The most common disilicates by far are members of the [[epidote]] group. Epidotes are found in variety of geologic settings, ranging from mid-ocean ridge to granites to [[pelite|metapelites]]. Epidotes are built around the structure [(SiO<sub>4</sub>)(Si<sub>2</sub>O<sub>7</sub>)]<sup>10−</sup> structure; for example, the mineral ''species'' epidote has calcium, aluminium, and ferric iron to charge balance: Ca<sub>2</sub>Al<sub>2</sub>(Fe<sup>3+</sup>, Al)(SiO<sub>4</sub>)(Si<sub>2</sub>O<sub>7</sub>)O(OH). The presence of iron as Fe<sup>3+</sup> and Fe<sup>2+</sup> helps buffer oxygen [[fugacity]], which in turn is a significant factor in petrogenesis.<ref name="DG612-627">{{harvnb|Dyar|Gunter|2008}}, pp. 612–27</ref>

Other examples of sorosilicates include [[lawsonite]], a  metamorphic mineral forming in the [[blueschist]] facies (subduction zone setting with low temperature and high pressure), [[vesuvianite]], which takes up a significant amount of calcium in its chemical structure.<ref name="DG612-627" /><ref>{{harvnb|Chesterman|Lowe|2008}}, pp. 565–73</ref>