Crystal structures of minerals are defined by a specific atomic arrangement within the unit‐cell, which follows the laws of symmetry specific to each crystal system. The causes for a mineral to crystallize in a given crystal system have been the subject of many studies showing their dependency on different formation conditions, such as the presence of aqueous fluids, biotic activity and many others. Different attempts have been made to quantify and interpret the information that we can gather from studying crystal symmetry and its distribution in the mineral kingdom. However, these methods are mostly outdated or at least not compatible for use on large datasets available today. Therefore, a revision of symmetry index calculation has been made in accordance with the growing understanding of mineral species and their characteristics. In the gathered data, we observe a gradual but significant decrease in crystal symmetry through the stages of mineral evolution, from the formation of the solar system to modern day. However, this decrease is neither uniform nor linear, which provides further implications for mineral evolution from the viewpoint of crystal symmetry. The temporal distribution of minerals based on the number of essential elements in their chemical formulae and their symmetry index has been calculated and compared to explore their behaviour. Minerals with four to eight essential elements have the lowest average symmetry index, while being the most abundant throughout all stages of mineral evolution. There are many open questions, including those pertaining to whether or not biological activity on Earth has influenced the observed decrease in mineral symmetry through time and whether or not the trajectory of planetary evolution of a geologically active body is one of decreasing mineral symmetry/increasing complexity.

The mineral kingdom has experienced dramatic increases in diversity and complexity through billions of years of planetary evolution as a consequence of a sequence of physical, chemical, and biological processes. Each new formational environment, or “mineral paragenetic mode,” has its own characteristic attributes, including the stage of mineral evolution and geological age, ranges of T, P, duration of formation events, and other environmental influences on mineral formation. Furthermore, the minerals associated with each paragenetic mode have a wide range of average properties, including hardness, density, and chemical and structural complexity. A survey of attributes of 57 mineral paragenetic modes representing the full range of mineral-forming processes reveals systematic trends, including: (1) minerals documented from older paragenetic processes are systematically harder on average than those from more recent processes; (2) minerals from paragenetic modes formed at lower T (notably <500 K) display greater average structural complexity than those formed at high T (especially >1000 K); and (3) minerals from paragenetic modes that display greater average chemical complexity are systematically less dense than those from modes with lesser average chemical complexity. In addition, minerals formed in anhydrous environments and/or by abiotic processes are, on average, significantly denser and harder than those formed in hydrous environments and/or by biotic processes.

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.

A survey of the average Mohs hardness of minerals throughout Earth’s history reveals a significant and systematic decrease from >6 in presolar grains to ~5 for Archean lithologies to <4 for Phanerozoic minerals. Two primary factors contribute to this temporal decrease in the average Mohs hardness. First, selective losses of softer minerals throughout billions of years of near-surface processing lead to preservational biases in the mineral record. Second, changes in the processes of mineral formation play a significant role because more ancient refractory stellar phases and primary igneous minerals of the Hadean/Archean Eon are intrinsically harder than more recently weathered products, especially following the Paleoproterozoic Great Oxidation Event and the production of Phanerozoic biominerals. Additionally, anthropogenic sampling biases resulting from the selective exploration and curation of the mineralogical record may be superimposed on these two factors.

&lt;p&gt;Characterizing the types of crystalline structures that form in different environments helps us to better interpret the geologic record and deepens our understanding of mineral stability. To this end, the Dolivo &amp;#8211; Dobrovol&amp;#8217;sky symmetry index provides a convenient way to quantify the statistical trends in the symmetry of minerals over time (Bermanec et al. 2022). Behavior of the Dolivo - Dobrovol&amp;#8217;sky symmetry index was investigated for different paragenetic modes of minerals (Hazen and Morrison 2022). Two datasets were used and compared (code and datasets are available on https://github.com/NoaVidovic/pgm-mineral-pairs-pg). The first one used only minerals, and each mineral was considered just once. In contrast, in the mineral&amp;#8211;paragenetic mode pair dataset, minerals were counted once for each of the paragenetic modes in which they occurred.&lt;/p&gt;&lt;p&gt;The paragenetic mode dataset incorporates a number of properties associated with each of more than 60 modes of formation, including relative age and order of that mode&amp;#8217;s first appearance, estimated minimum and maximum temperature and pressure of formation, and duration. Paragenetic mode order does not substantially affect the symmetry index of minerals. However, some trends are evident when inspecting the properties of given paragenetic modes. The symmetry indices show a strong correlation with the maximum temperature, maximum pressure, and minimum pressure of paragenetic modes they belong to (Hazen et al. 2022) with correlation coefficients of 69%, 84% and 95%, respectively when using the mineral dataset. These trends show that minerals formed at higher temperature display higher overall symmetry. Trends for pressure are enigmatic: correlations show that minerals formed at higher minimum pressure tend to favor lower symmetry, whereas minerals formed at higher maximum pressure tend to favor higher symmetry.&lt;/p&gt;&lt;p&gt;When using the mineral&amp;#8211;paragenetic mode dataset, the correlation coefficients are significantly lower at 42%, 30% and 89% for maximum temperature, maximum pressure, and minimum pressure, respectively. The lower correlation coefficients obtained using the mineral&amp;#8211;paragenetic mode pairs might indicate that the paragenetic mode is not as important in terms of trends in symmetry as initially thought. On the other hand, considering a much higher correlation coefficient for the mineral dataset, perhaps there is a more dominant effect where certain P-T conditions tend to favor certain types of symmetry at equilibrium.&lt;/p&gt;