The Use of Chemical-Element Adjectival Modifiers in Mineral Nomenclature

Chemical-element adjectival modifi ers are not part of the name of a mineral species. Schaller-type adjectival modifi ers, which have the endings-oan or-ian, formerly recommended by the CNMMN of the IMA, in many cases give erroneous information about the valence of an ion, and are therefore inappropriate. Instead of such modifi ers, the CNMMN has now approved a proposal that chemical-element adjectival modifi ers employing the chemical-element symbol or the name of the chemical element together with a descriptive term should be used. The valence (nominal numerical charge plus sign) or the numerical oxidation state may be added, if required. Authors should therefore feel free to use chemical-element adjectival modifi ers that are chemically correct and that meet their particular requirements. For example, chemical-element adjectival modifi ers such as “Mg-rich”, “Mg–Fe-rich”, “Fe2+-poor”, “iron(2+)-enriched”, “iron(II)-bearing”, “alkali-defi cient”, “sodium-exchanged”, “Cr-doped”, or “H2O-saturated” may be used. Synthetic or hypothetical analogues of mineral species or natural analogues of mineral species unapproved by the CNMMN could be written with a chemical-element(s) suffi x. The synthetic product “topaz-OH ” is the OH-dominant analogue of topaz, Al2SiO4F2. The use of quotation marks around “topaz-OH ” is essential to show that the name is not approved by the CNMMN and to avoid confusion with names of real mineral species, such as chabazite-Ba. A chemical-element symbol should not be used as a prefi x to a name of a mineral species. However, if used in a diagram, table, or running heading owing to space limitations, then a correct version must be used in the text together with the short version in quotation marks to show that the