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# Lumping and splitting: Toward a classification of mineral natural kinds

## Details

**Authors** Hazen, Robert M. and Morrison, Shaunna M. and Krivovichev, Sergey V. and Downs, Robert T.

**Year** 2022

**Publisher** American Mineralogist

**Kind of work** article

**Discipline** Geology

**Secondary disciplines** Chemistry, Materials Science

**Applied** false

[Read it at the publisher](https://doi.org/10.2138/am-2022-8105) 
10.2138/am-2022-8105

## In authors' words

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

To propose explicit rules for lumping and splitting the species approved by the International Mineralogical Association, so that minerals can be classified as natural kinds.

### Who or what was studied (sample)

The 5,659 mineral species approved by the International Mineralogical Association.

### How they did it (methods)

The authors apply three lumping criteria to the approved species and two splitting criteria (distinct paragenetic modes, and cluster analysis of specimen attributes), then count the resulting kinds.

### What they found (results)

About 41% of the 5,659 approved species can be lumped with others, giving 4,016 root mineral kinds. Adding paragenetic modes yields 7,816 preliminary natural kinds, and the authors estimate that Earth holds more than 10,000 mineral natural kinds. They acknowledge that lumping and splitting decisions remain partly subjective.

## Commentary

### In short

The authors show that the official list of mineral species can be regrouped by explicit rules into a smaller set of root kinds. They then divide those by formation process into a larger set of natural kinds.

### Response

The paper turns on where to draw category boundaries (D). Species defined by idealized end-member composition and structure are merged where solid solution is continuous and split where formation processes differ, which is a decision about what counts as one kind and what counts as another. The lumping criteria also place species inside larger groupings such as solid-solution series and homologous series (S). Caveats: the authors do not use these terms, the fit to S is looser than the fit to D, and they state that their own boundary decisions remain subjective.

**Patterns it shows** D, S

Shows the structure is there

**Added** 2026-10-12

**How to cite this** Hazen, Robert M. and Morrison, Shaunna M. and Krivovichev, Sergey V. and Downs, Robert T. (2022). Lumping and splitting: Toward a classification of mineral natural kinds. American Mineralogist.