CNMNC guidelines for the use of suffixes and prefixes in mineral nomenclature, and for the preservation of historical names

New CNMNC guidelines are established, in order to standardize the use of prefixes and suffixes in mineral nomenclature, and to preserve historical names. The recommendations for the use of suffixes are: (I) chemical suffixes have to be in parentheses, except for extra-framework cations; (II) a maximum of three chemical suffixes is allowed; (III) cations and anions should never be used together in the parentheses. For the use of prefixes, the following guidelines were adopted: (I) for common names, prefix-type nomenclature is preferred to facilitate the pronunciation; (II) an unnecessary proliferation of prefixes must be avoided, and a maximum of three chemical prefixes is recommended; (III) it is allowed to use a combination of chemical, structural or other descriptive prefixes; (IV) when Levinson modifiers are used as suffix for REE, then other cations or anions have to be placed as a prefix; (V) in case of polytypes and topologically similar polymorphs, a chemical prefix-type nomenclature is preferred, since the polytype and polymorph symbols have to be suffixes. When possible, the CNMNC recommends to avoid changing names, especially for grandfathered species. Well-established mineral names or names dedicated to localities or persons have to be preserved, except if the species is shown to be not valid. Historical names cannot be changed in order to standardize the nomenclature of a group or supergroup, since mixed nomenclature systems are now accepted by the CNMNC.