The Taxonomy of Mineral Occurrence Rarity and Endemicity

Abstract

Nearly a half of known IMA-approved minerals (as of November 2021) are reported from four localities or fewer and so may be considered rare mineral species. These minerals form a continuum with more common species (e.g., rock-forming minerals), all of which constitute important constituents of Earth and contributors to its dynamics. To better understand the taxonomy of mineral rarity, evaluations have been made on the basis of k-means clustering and kernel density estimation of one-dimensional data on mineral occurrence metrics. Results from second- and third-degree polynomial regression analyses indicate the presence of a divergence between the observed number of endemic minerals discovered since 2000 and those that are likely to represent “true” endemic species. The symmetry index, calculated using the approach of Urusov for each rarity cluster, reveals a gradual decrease from ubiquitous to endemic from 0.64 to 0.47. A network analysis of element co-occurrences within each rarity cluster suggests the existence of at least three different communities having similar geochemical affinities; the latter may reflect the relative abundance of minerals their elements tend to form. The analysis of element co-occurrence matrices within each group indicates that crustal abundance is not the only factor controlling the total number of minerals each element tends to form. Other significant factors include: (1) the geochemical affinity to the principal element in the group (i.e., sulfur for chalcophile and oxygen for lithophile elements) and (2) dispersion of the principal element through geochemical processes. There is a positive correlation between the lithophile element group's abundance in the Earth's crust and the number of common minerals they tend to form, but a negative correlation with the number of rare species.

The Average Symmetry Index of Minerals Co-Varies with Their Hydrogen Content, Rarity, and Paragenetic Mode

“…Urusov [16] explained the gradual drop of symmetry throughout Earth's history as a consequence of an increase in the number of rare (presumably on average of lower symmetry) species of minerals. While this "dissymmetrization" trend is present, and further confirmed by Gavryliv et al [17], it does not explain the root cause for the symmetry decrease. These ideas were further expanded by Urusov [18] with examples of reactions where products have a lower symmetry than the reactant minerals.…”

“…The distinct behavior and impact of common minerals compared to rare ones have been discussed by Hazen and Ausubel [23]. Interestingly, Gavrilyv et al [17] observed that as rarity increases, symmetry indices decrease while the complexity of minerals increases. Although the reciprocal relationship between symmetry indices and mineral complexity is well documented, it has not yet been quantified in the works of Krivovichev and colleagues [21,[25][26][27][28][29].…”

Classifying minerals and their related names in a relational database

“…The context can be present for all categories but essential only for officially regulated mineral and rock names. The historical and social context can be used to trace mineral discoveries' spatial and temporal evolution (Ponomar, in press) that was shown to impact the mineral rarity classification (Gavryliv et al, 2022b). ( 2) Compositional context includes idealized and empirical mineral formulas, ions, elements, impurities, inclusions, and intergrowth material.…”

“…The context can be present for all categories but essential only for officially regulated mineral and rock names. The historical and social context can be used to trace spatial and temporal evolution of mineral discoveries (Ponomar, 2023) that was shown to impact the mineral rarity classification (Gavryliv et al, 2022b).…”

On the Diversity and Formation Modes of Martian Minerals

“…Related to these processes are the profound effects of the selection and concentration by water/rock interactions of more than 40 rare elements that collectively represent only 0.01% of crustal atoms in Earth, yet are essential to more than 40% of Earth's mineral diversity-a finding that echoes the observation that most terrestrial minerals are volumetrically trivial and rare (Gavryliv et al, 2022;Hazen & Ausubel, 2016;Hazen et al, 2015;Hystad et al, 2015). Most of these rare-element minerals are not expected on Mars.…”