AbstractThe Subcommittee for Unnamed Minerals of the IMA Commission on New Minerals, Nomenclature and Classification (CNMNC, formerly CNMMN) has developed a codification system that includes the year of publication and qualitative chemical composition for unnamed minerals reported in the literature. Such minerals are divided into two categories: (1) those regarded as being ‘valid as unnamed minerals’ are those that do not correspond to existing species, have not been reported previously and whose published descriptions enable them to be recognized if found elsewhere. (2) Unnamed minerals regarded as being ‘invalid as unnamed minerals’ are those whose published descriptions are inadequate for their confident recognition if found elsewhere, or which correspond to existing mineral species or unnamed minerals published previously.