Minerals incorporate 72 different essential elements, many of which are redox sensitive. We compiled oxidation states of ions in 4834 IMA-approved mineral species with oxygen and/or halogens as anions and have identified 87 essential mineral-forming ions. We compiled data on the coexistence of these ions as recorded in their minerals’ chemical formulas, and applied methods of network analysis with community detection and heatmap analysis with agglomerative clustering to reveal patterns of ion coexistence.
Unipartite networks illustrate the most common coexisting ion pairs, whereas Louvain and Walktrap methods reveal distinct ion groups—patterns that both reinforce and refine the Goldschmidt geochemical classification of elements. Key findings include: (1) that mineral-forming ions group into two major communities with a number of subcommunities; (2) that different ion communities primarily reflect contrasting geochemical and paragenetic processes such as primary igneous mineralisation, hydrothermal precipitation, and near-surface oxidation and weathering, rather than crystal chemical constraints; and (3) that different oxidation states of some redox-sensitive elements fall into two or more of these communities, underscoring how ions of the same elements commonly display contrasting geochemical and/or paragenetic affinities.
Heatmap analysis reveals groupings of co-occurring ions that mimic many aspects of community detection methods, as well as significant patterns of ion antipathies—groups of ions that are seldom if ever paired. For example, alkali metals commonly associated with late-stage igneous fluids (Cs+, Li+ and Rb+) rarely co-occur with low field strength ions found concentrated in brines (Ag+, Br–, Cu+, Hg+ and I–) or high field strength ions from weathered primary oxide or sulfide deposits (Cr6+, Pb4+, Mo4+, Te4+ and Te6+). Such ion pairs are well known in synthetic oxides. Therefore, with the exceptions of cations having very different redox potentials, unobserved ion pairs are principally the consequences of element rarity coupled with natural geochemical and paragenetic antipathies rather than crystal chemical constraints.
