Variation of physical properties across the mineralogical system

Abstract

This work was undertaken to investigate whether physical data exhibit any tendencies spanning the whole mineralogical system. The chemical compositions of 4973 minerals was projected into two variables, Qual_4 and InfEnt, the first a function of the atomic numbers of elements present, the second, an indication of complexity of their stoichiometry. As the Z coordinates served density (1933 minerals and 476 ICSD entries); reflectance (565); mean refractive index (3001); and Vickers hardness VHN (462), all of them on logarithmic scale. Planes fitted to the first three datasets exhibit a pronounced increase with increasing atomic numbers of elements present (Qual_4) and a mild decrease with the complexity of formulae (InfEnt). Contrariwise, the VHN set indicates a decrease with Qual_4 and an increase along the InfEnt axis. A set of 732 mean refractive indices (Shannon and Fischer in Am Miner 101:2288-2300, 2016) indicates an increase with Qual_4 but a mild increase (not decrease) along the InfEnt axis. There is considerable scatter in all plots, but regression equations presented here allow anyone to calculate rather rough estimates of physical data based on input chemical coordinates Qual_4 and InfEnt. The mineralogical interpretation of the results remains open; this is a first attempt.