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# On the application of the IMA−CNMNC dominant-valency rule to complex mineral compositions

## Details

**Authors** Bosi, Ferdinando and Hatert, Frédéric and Hålenius, Ulf and Pasero, Marco and Miyawaki, Ritsuro and Mills, Stuart J.

**Year** 2019

**Publisher** Mineralogical Magazine

**Kind of work** article

**Discipline** Geology

**Secondary disciplines** Chemistry

**Applied** false

[Read it at the publisher](https://doi.org/10.1180/mgm.2019.55) 
10.1180/mgm.2019.55

## In authors' words

### What they set out to do (purpose)

To set out how mineral species should be identified from complex compositions using an end-member formula and the dominant-valency rule.

### How they did it (methods)

A nomenclature procedure approved by the IMA Commission on New Minerals, Nomenclature and Classification in May 2019, with a complementary site-total-charge approach for cases the rule does not handle.

### What they found (results)

The commission strongly recommends the dominant-valency rule for mineral nomenclature. The authors note that the dominant-end-member approach can be ambiguous because end-member proportions depend on the sequence of calculation. The dominant-valency rule can produce unbalanced end-member formulae when a coupled heterovalent substitution occurs at two sites alongside a substitution at a single site; in those cases they propose the site-total-charge approach.

## Commentary

### In short

The international body that names minerals sets out a rule for deciding which species a complex mineral composition belongs to, and a fallback method for the cases where the rule gives an unbalanced formula.

### Response

Species assignment is a matter of drawing category boundaries in compositional space, and the paper shows the boundary depends on the rule used: the older dominant-end-member approach gives sequence-dependent answers. The composition is analyzed as a whole built from crystallographic sites and the constituents occupying them, with end-members as the component parts, so part–whole structure carries the argument. Relationship (coupled substitution between sites) enters only as the case that breaks the rule. The abstract and publisher page were the only sources, so the fit rests on the authors' summary and not on the full derivation.

**Patterns it shows** D, S

Formal proof or model

**Added** 2026-11-02

**How to cite this** Bosi, Ferdinando and Hatert, Frédéric and Hålenius, Ulf and Pasero, Marco and Miyawaki, Ritsuro and Mills, Stuart J. (2019). On the application of the IMA−CNMNC dominant-valency rule to complex mineral compositions. Mineralogical Magazine.