Volume 104, Issue 5

Arsenic and antimony are highly toxic to humans, animals, and plants. Incorporation in alunite, jarosite, and beudantite group minerals can immobilize these elements and restrict their bioavailability in acidic, oxidizing environments. This paper reviews research on the magnitude and mechanisms of incorporation of As and Sb in, and release from, alunite, jarosite, and beudantite group minerals in mostly abiotic systems. Arsenate-for-sulfate substitution is observed for all three mineral groups, with the magnitude of incorporation being beudantite (3–8.5 wt% As) > alunite (3.6 wt% As) > natroalunite (2.8 wt%) > jarosite (1.6 wt% As) > natroalunite (1.5 wt% As) > hydroniumalunite (0.034 wt% As). Arsenate substitution is limited by the charge differences between sulfate (–2) and arsenate (–3), deficiencies in B-cations in octahedral sites and for hydroniumalunite, difficulty in substituting protonated H 2 O-for-OH- groups. Substitution of arsenate causes increases in the c -axis for alunite and natroalunite, and in the c - and a -axes for jarosite. The degree of uptake depends on, but limited by, the AsO 4 /TO 4 ratio. Aerobic and abiotic As release from alunite and natroalunite is limited, especially between pH 5 and 8. Release of As is also very limited in As-bearing jarosite, natrojarosite, and ammoniumjarosite at pH 8 due to the formation of secondary maghemite, goethite, hematite, and Fe arsenates that resorb the liberated As. Abiotic reductive dissolution of As-bearing jarosite at pH 4, 5.5, and 7 is likewise restricted by the formation of secondary green rust sulfate, goethite, and lepidocrocite that take up the As. Similar processes have been observed for the aerobic dissolution of Pb-As-jarosite (beudantite analog), with secondary Fe oxyhydroxides resorbing the released As at pH 8. Higher amounts of As are released, however, during microbial-driven jarosite dissolution. Natural jarosite has been found to contain up to 5.9 wt% Sb 5+ substituting for Fe 3+ in the B-site of the mineral structure. Sb(V) is not released from jarosite at pH 4 during abiotic reductive dissolution, but at pH 5.5 and 7, up to 75% of the mobilized Sb can be structurally incorporated into secondary green rust sulfate, lepidocrocite, or goethite. Further research is needed on the co-incorporation of As, Sb, and other ions in, and the uptake and release of Sb from, alunite, jarosite, and beudantite group minerals, the influence of microbes on these processes and the long-term (>1 yr) stability of these minerals.

Patterns in the discovery and description of new minerals over the last century emerge from a new database of 4046 mineral discovery reports (roughly ¾ of all known minerals). The number of new minerals discovered per year was steady over time from 1917 to the early 1950s, when it began a rapid increase punctuated by spikes in 1962–1969, 1978–1982, and 2008–2016, the last of which is probably still ongoing. A detailed breakdown of the technological, geographic, institutional, and other characteristics of mineral discovery in this data set elucidates factors leading to increases in mineral discovery. (1) The availability of instrumentation for a particular analytical technique has a far larger impact on the rate of its uptake in mineral discovery than the technique’s invention or computer automation. (2) Samples from mines, quarries, and resource exploration have produced around 2⁄3 of all new mineral discoveries due to geochemical peculiarity and good exposure; lunar and meteoritic samples have contributed relatively few new minerals. (3) Peralkaline intrusions and volcanic fumaroles are the next most productive sites of new mineral discovery. (4) Which countries host mineralogists who discover large numbers of new minerals have varied over time but is always a relatively small number (<20), and mineral discovery is highly concentrated in specific laboratories or workgroups. (5) Involvement of governmental organizations in new mineral discovery peaked in the aftermath of World War II and has since declined to almost nil, with new mineral discoveries now coming primarily from universities and similar academic institutions (75%) and from museums (25%). (6) The average number of authors on mineral discovery papers has risen from <1.5 in 1950 to >6 now and follows an exponential trend. (7) The average number of methods used to characterize new minerals has not changed significantly since 1960, and about half of new mineral descriptions are made using roughly the minimum of analyses required for a new mineral to be recognized. (8) A partial study of discredited or redefined minerals identified changes to nomenclature and classification as the primary causes for discreditation; failure to replicate analytical results is a distant second. Only five cases of fraudulent mineral discovery are known. This article presents the data underlying these analyses and discusses some possible reasons for the observed trends in the rate of new mineral discovery, as well as the implications for the history (and future) of mineralogy.

The milky appearance shown by certain type IaB diamonds has been subjected to several recent studies, but the origin of this feature is not fully understood. Here several type IaB diamonds with a milky appearance have been studied by cathodoluminescence (CL), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). CL of several hazy type IaB diamonds shows scattered or orientated micro-sized spots or short linear luminescence features. TEM observation revealed that those spots and linear features are caused by dislocation loops that are likely responsible for the hazy appearance of the host diamonds. It is also shown that type IaB diamonds with a cloudy appearance contain nano-sized inclusions with negative crystals of octahedral shape. Some of these negative crystals contain a precipitate that can be explained by a compressed disordered cubic δ-N 2 phase observed by high-resolution TEM. In one of the milky IaB diamonds with platelet defects, polycrystalline areas composed of columnar diamond crystals elongated radially in [110], similar to ballas diamond, were revealed by EBSD. Taking into account these observations, it is suggested that the dislocation loops, nano-sized inclusions (negative crystals) and/or characteristic grain boundaries of the radiating fibrous crystals would be the origins for the milky appearance of the type IaB diamonds studied here. Those results add a complementary explanation that accounts for the milkiness of type IaB diamonds studied before.

Subvolcanic phonolite intrusions of the Kaiserstuhl Volcanic Complex (Germany) show variable degrees of alteration. Their secondary mineralogy has been characterized by petrographic textural observations, bulk-rock powder X‑ray diffraction, thermogravimetry, differential thermal analysis, and electron probe microanalysis. The alteration assemblage is dominated by various zeolites that occur in fissures, vugs, and as replacement products of primary phases within the phonolite matrix. Phonolites in the eastern Kaiserstuhl were emplaced into a sedimentary sequence and are characterized by high zeolite contents (Endhalden: 48 wt%, Fohberg: 45 wt%) with the temporal sequence: ± thomsonite-Ca ± mesolite – gonnardite – natrolite – analcime. In the western Kaiserstuhl zeolite contents are lower (Kirchberg: 26 wt% or less) and the crystallization sequence is: ± thomsonite-Ca – gonnardite – natrolite – chabazite-Ca. Pseudomorphic replacement textures and barite inclusions in secondary aggregates suggest that zeolites grew at the expense of a sulfate-bearing sodalite-group mineral, i.e., haüyne. Fresh grains of sodalite-haüyne are only found at Kirchberg, whereas the pervasive alteration at Fohberg and Endhalden transformed feldspathoid minerals completely to zeolites. Zeolites formed in a continuously cooling hydrothermal regime after emplacement and solidification of phonolitic magmas. The common paragenetic sequence corresponds to a decrease in the Ca/Na ratio, as well as an increase in the Si/Al ratio with time. The shift from Ca-Na- to pure Na-zeolites is an expression of closed-system behavior in a water-rich environment at Fohberg and Endhalden, which both intruded an Oligocene pre-volcanic sedimentary unit. The late crystallization of K-bearing chabazite-Ca points to a progressively more open hydrothermal system in the Kirchberg phonolite, which was emplaced in a subaerial volcanic succession and was influenced by K-enriched fluid from leucite-bearing country rock. Therefore, the geological setting and nature of emplacement are important factors that control the degree of zeolitization of intrusive feldspathoid minerals-bearing rocks and whether a zeolite occurrence can be used as mineral deposit.

The melting point of barium carbonate (BaCO 3 ) was determined at pressures up to 11 GPa using the ionic conductivity and platinum (Pt) sphere methods in a multi-anvil press. The melting point decreases with pressure from 2149 ± 50 K at 3 GPa to a fitted local minimum of 1849 K at 5.5 GPa, and then it rises with pressure to 2453 ± 50 K at 11 GPa. The fitted melting curve of BaCO 3 based on the ionic conductivity measurements is consistent with the Pt sphere measurements that were carried out independently at selected pressures. The negative slope of the BaCO 3 melting curve between 3 and 5.5 GPa indicates that the liquid is denser than the solid within this pressure range. Synchrotron X‑ray diffraction (XRD) measurements in a laser-heated diamond-anvil cell (LH-DAC) showed that BaCO 3 transformed from the aragonite structure ( Pmcn ) to the post-aragonite structure ( Pmmn ) at 6.3 GPa and 1026 K as well as 8 GPa and 1100 K and the post-aragonite structure remained metastable upon quenching and only reverted back to the witherite structure upon pressure release. The local minimum near 5 GPa is attributed to the triple point where the melting curve of BaCO 3 meets a phase transition to the denser post-aragonite structure ( Pmmn ). Local minima in the melting curves of alkaline earth carbonates would lead to incipient melting of carbonated rocks in Earth’s mantle.

The elasticity of a sequence of SiO 2 -TiO 2 glasses is examined at high pressures and temperatures. A primary goal is to determine how the previously proposed substitution of fivefold-coordinated Ti at low concentrations of Ti and fourfold-coordinated Ti at higher concentrations affects the elastic properties of these glasses. The effect of changing Ti content on the bulk moduli of these glasses is monotonic, and no systematic effect of possible coordination changes is observed. In contrast, there is an apparent decrease in the pressure derivative of the bulk modulus above ~3 wt% TiO 2 . This change occurs at a similar composition to that at which a transition from predominantly fivefold to fourfold of Ti has been proposed to occur in these glasses. Hence, this shift in the pressure derivative of the bulk modulus is attributed to a stiffening of the equation of state of these glasses generated by the substitution of fivefold Ti species relative to TiO 4 units. Our results provide rationales for the onset of coordination changes producing a minimal change in the equation of state of silicate melts/glasses, and for bulk moduli determined at ambient pressure producing relatively accurate silicate melt volumes even within liquids that have begun to undergo coordination changes. Thus, our results support the general validity of single equation of state formulations that describe the densities of silicate melts through the transition zone and shallow lower mantle.

Nanoparticles are widely present in the natural environment. Their surface reactivity, redox ability, and adsorption properties are related to geochemical processes. To explore the thermodynamics of interaction between nano oxides and small gas molecules, we applied gas adsorption calorimetry to investigate the energetics of ethanol and carbon dioxide adsorbed on surfaces of nanoscale anatase, rutile, and γ-alumina particles. The measured zero-coverage adsorption enthalpies per mole of gas adsorbed are –97.7, –107.3, and –84.8 kJ/mol for C 2 H 5 OH on anatase, rutile, and γ-Al 2 O 3 , respectively. The corresponding values for CO 2 adsorption are –59.4, –47.4, and –47.1 kJ/mol. The results indicate the ethanol adsorption is generally more exothermic than carbon dioxide and water adsorption. The isotherm and differential enthalpies show type II isotherms and step-wise patterns for ethanol adsorption in all three oxides. However, CO 2 adsorption shows simple continuous isotherms and energetics that suggest dominant physical adsorption occurred. The repeated adsorption cycle shows that ethanol adsorption on these nanoparticles is partially reversible at room temperature. This thermodynamic evidence indicates that ethanol and similar organics may protect mineral oxide surfaces from reaction with aqueous solutions, which may affect crystal growth, dissolution, and biomineralization.

Although nucleation of magnetite and/or hematite along dislocations upon oxidation of olivine has been observed by many workers, the effect of oxidation on the magnetic properties of the sample with specific mineralogical alterations has not been studied. Therefore, we investigate this problem using a set of time series 1 bar oxidation experiments at 600 and 900 °C. Results show rapid olivine oxidation and alteration at both 600 and 900 °C, forming magnetite and hematite associated with a change from paramagnetic to ferromagnetic behavior after oxidation. Magnetite and hematite nucleate along dislocations and impurities in the crystal structure, along with surface coatings and within cracks in the crystals. Fresh, unaltered mantle xenoliths containing magnetite have been interpreted as having formed in cold tectonic regimes in the mantle, rather than through oxidation during or after ascent. Mantle xenoliths rapidly ascend through the mantle with estimates of the ascent of up to 90 km/h (3 GPa/h) based on the diffusion profile of water in mantle olivine. The rates correspond to xenoliths ascending through the mantle over hours and not days or weeks. Our results show that olivine oxidation and alteration can occur in days to weeks at 600 °C and within minutes at 900 °C. Therefore, if the xenolithic material is transported to the surface in a cold magma (at temperatures ≤600 °C), then the timescale of ascent is likely not long enough for oxidation to cause magnetite formation or a ferromagnetic signature to occur. However, if the material is transported in a hot oxidized basaltic magma (with temperatures ≥900 °C), then oxidation can cause magnetite formation and a ferromagnetic signature.

We report on a systematic study on the physicochemical attributes of synthetic Fe-Cu-sulfide nanoparticles (NPs) precipitated under conditions similar to the anoxic, low-temperature aqueous, sedimentary, soil, and subsurface environments where these NPs have been repeatedly identified. Characterizing the basic attributes of these NPs is the first step in understanding their behaviors in various processes including in the bio-availability of essential and toxic metals, environmental remediation, and resource recovery. Abiotic experiments are compared to biotic experiments in the presence of the sulfate-reducer Desulfovibrio vulgaris to elucidate biological controls on NP formation. First, the single-metal end-member NPs are determined by precipitation in a solution containing either aqueous Fe(II) or Cu(II). Limited differences are observed between biogenic and abiogenic precipitates aged for up to one month; the Fe-only experiments resulted in 4–10 nm mackinawite (FeS) NPs that aggregate to form nanosheets up to ~1000 nm in size, while the Cu-only experiments resulted in mixtures of covellite (CuS) NPs comprised of <10 nm fine nanocrystals, 20–40 × 6–9 nm nanorods, and ~30 nm nanoplates. The crystal sizes of biogenic mackinawite and covellite are, respectively, larger and smaller than their abiogenic counterparts, indicating a mineral-specific response to biological presence. Structural defects are observable in the fine nanocrystals and nanorods of covellite in both biogenic and abiogenic experiments, indicative of intrinsic NP instability and formation mechanism via particle attachment. In contrast, covellite nanoplates are defect free, indicating high stability and potentially rapid recrystallization following particle attachment. Next, mixed-metal sulfide NPs are precipitated at variable initial aqueous Fe-to-Cu ratios (2:1, 1:1, and 1:5). With an increasing ratio of Fe-to-Cu, Fe-rich covellite, nukundamite (Cu 5.5 FeS 6.5 ), chalcopyrite (CuFeS 2 ), and Cu-rich mackinawite are formed. The Fe-rich covellite NPs are larger (100–200 nm) than covellite precipitated in the absence of Fe, indicating a role for Fe in promoting crystal growth. Chalcopyrite and nukundamite are formed through the incorporation of Fe into precursor covellite NPs while retaining the original crystal morphology, as confirmed by doping a covellite suspension with aqueous Fe(II), resulting in the formation of chalcopyrite and nukundamite within days. Additionally, in the biological systems, we observe the recrystallization of mackinawite to greigite (Fe 3 S 4 ) after six months of incubation in the absence of Cu and the selective formation of chalcopyrite and nukundamite at lower initial Fe-to-Cu ratios compared to abiotic systems. These observations are consistent with NP precipitation that are influenced by the distinct (sub)micro-environments around bacterial cells compared to the bulk solution. Comparative TEM analyses indicate that the synthetic NPs are morphologically similar to NPs identified in natural environments, opening ways to studying behaviors of natural NPs using experimental approaches.

The pressure-volume-temperature ( P-V-T ) measurements of the B2 (CsCl-type) phase of KCl were performed at 9–61 GPa/1500–2600 K and up to 229 GPa at room temperature, based on synchrotron X‑ray diffraction measurements in a laser-heated diamond-anvil cell (DAC). The nonhydrostatic stress conditions inside the sample chamber were critically evaluated based on the platinum pressure marker. With thermal annealing by laser after each pressure increment, the deviatoric stress was reduced to less than 1% of the sample pressure even at the multi-megabar pressure range. The obtained P-V-T data were fitted to the Vinet equation of state with the Mie-Grüneisen-Debye model for thermal pressure. The thermal pressure of KCl was found to be as small as ~10 GPa even at 3000 K at any given volume, which is only half of that of common pressure markers (i.e. Pt, Au, or MgO). Such a low-thermal pressure validates the use of a KCl pressure medium as a pressure marker at high temperatures.

The petrology, mineralogy, and geochemistry of lawsonite blueschists from the Tavşanlı zone in northwest Turkey—one of the best-preserved blueschist terranes in the world—have been comprehensively investigated. The blueschist samples contain lawsonite + sodic amphibole + phengite + chlorite + titanite + apatite ± aragonite ± quartz ± relict igneous pyroxene ± Mn-rich garnet and opaque phases. Lawsonite is a significant repository for Sr, Pb, Th, U, and REE, whereas phengite carries the most large-ion lithophile element (LILE), titanite hosts the highest Nb and Ta as well as considerable amounts of high field strength element (HFSE), and apatite strongly controls Sr. Two groups of blueschist have different origins—enriched continent-derived terrigenous origin and mid-ocean ridge basalts (MORB)-like submarine basalts—assigned on the basis of whole-rock major and trace element compositions and initial Sr-Nd-Pb isotopic results. Lawsonite in blueschist with enriched origin exhibits strong Th/La fractionation, raising the possibility of the involvement of blueschist facies mélange to explain the origin of Mediterranean potassium-rich magmatism because similarly high Th/La ratios are also observed in the Mediterranean potassium-rich lavas. We propose that subduction-induced tectonic imbrication took place entirely at shallow depths (<80 km), giving rise to a newly formed lithosphere where oceanic and continental crustal materials, sediments, strongly depleted peridotite blocks, and metamorphic rocks are all imbricated together, and in which many of the compositional characteristics of the lawsonite blueschist are sequestered. Subsequent melting of the fertile and enriched components in this new lithosphere would result in the generation of potassium-rich post-collisional mafic magmas with diagnostic geochemical affinities.

A calc-silicate rock from part of the Chotanagpur Granite Gneiss Complex, East India, develops veins and patches of vesuvianite (F: 2.3–3.9 apfu, Fe 3+ : 1.7–2.1 apfu) and garnet (Gr 71–80 Alm 12–17 Adr 1–9 ) proximal to amphibole-bearing quartzo-feldspathic pegmatitic veins. The host calc-silicate rock exhibits a prominent gneissic banding that is defined by alternate clinopyroxene- and plagioclase-rich layers. The vesuvianite-garnet veins are both parallel and cross-cutting the gneissic banding of the host calc-silicate rock. Two contrasting mineralogical domains that are rich in garnet and vesuvianite, respectively, develop within the vesuvianite-garnet veins. Textural studies support the view that the garnet- and vesuvianite-rich domains preferentially develop in the clinopyroxene- and plagioclase-rich layers of the host calc-silicate rocks, respectively. Some of the vesuvianite-rich domains of the veins develop the assemblage vesuvianite + quartz + calcite + anorthite (as a result of the reaction diopside + quartz + calcite + anorthite = vesuvianite) that was deemed metastable in the commonly used qualitative isobaric T - X CO2 topology in the system CaO-MgO-Al 2 O 3 -SiO 2 -H 2 O-CO 2 (CMASV). Using an internally consistent thermodynamic database, quantitative petrogenetic grids in the P-T and isobaric T - X CO2 spaces have been computed in the CMASV system. The influence of the non-CMASV components (e.g., Na, Fe 3+ , F) on the CMASV topologies have been discussed using the published a-X relations of the minerals. Our study shows topological inversion in the isobaric T-X CO2 space that primarily depends upon the composition of the vesuvianite. The quantitative CMASV topologies presented in this study successfully explain the stabilities of the natural vesuvianite-bearing assemblages including the paradoxical assemblage vesuvianite + quartz + calcite + anorthite. Application of the activity-corrected CMASV topology suggests that infiltration of F-bearing oxidizing aqueous fluids into the calc-silicate rocks develop the vesuvianite-garnet veins in the studied area. A genetic link between quartzo-feldspathic pegmatites and the vesuvianite-garnet veins seems plausible. This study demonstrates controls of topological inversion in the complex natural system, owing to which certain mineral assemblages develop in nature that are otherwise deemed metastable in one set of reaction geometry.

Large-ion lithophile elements (LILE)-enriched chromium titanates of the magnetoplumbite (AM 12 O 19 ) and crichtonite (ABC 18 T 2 O 38 ) groups have been recognized as abundant inclusions in orthopyroxene grains in a mantle-derived xenolith from the Udachnaya-East kimberlite pipe, Daldyn field, Siberian craton. The studied xenolith consists of three parts: an orthopyroxenite, a garnet clinopyroxenite, and a garnet-orthopyroxene intermediate domain between the two. Within the host enstatite (Mg# 92.6) in the orthopyroxenitic part of the sample titanate inclusions are associated with Cr-spinel, diopside, rutile, Mg-Cr-ilmenite, and pentlandite. Crichtonite-group minerals also occur as acicular inclusions in pyrope grains of the intermediate domain adjacent to the orthopyroxenite, as well as in interstitial to enstatite oxide intergrowths together with Cr-spinel, rutile, and ilmenite. Yimengite-hawthorneite inclusions in enstatite contain (wt%) 3.72–8.04 BaO, 2.05–3.43 K 2 O, and 0.06–0.48 CaO. Their composition is transitional between yimengite and hawthorneite end-members with most grains exhibiting K-dominant chemistry. A distinct feature of the studied yimengite-hawthorneite minerals is a high content of Al 2 O 3 (5.74–7.69 wt%). Crichtonite-group minerals vary in compositions depending on the occurrence in the xenolith: inclusions in enstatite are moderate-high in TiO 2 (62.9–67.1 wt%), moderately Cr-rich (12.6–14.0 wt% Cr 2 O 3 ), Ba- or K-specific in the A site, and contain low ZrO 2 (0.05–1.72 wt%), whereas inclusions in pyrope are moderate in TiO 2 (61.7–63.3 wt% TiO 2 ), relatively low in Cr (8.98–9.62 wt% Cr 2 O 3 ), K-dominant in the A site, and are Zr-enriched (4.64–4.71 wt% ZrO 2 ). Crichtonite-group minerals in polymineralic oxide intergrowths show highly diverse compositions even within individual aggregates, where they are chemically dominated by Ba, Ca, and Sr. P-T estimates indicate the orthopyroxenite to have equilibrated at ~800 °C and 35 kbar. Preferentially oriented lamellae of enstatite-hosted Cr-spinel and diopside, as well as pyrope, diopside, and Cr-spinel grains developed around enstatite crystals, are interpreted to have been exsolved from the high- T Ca-Al-Cr-enriched orthopyroxene precursor. The exotic titanate compositions and observed textural relationships between inclusions in enstatite imply that the studied orthopyroxenite has undergone metasomatic processing by a mobile percolating agent afterward; this highly evolved melt/fluid was enriched in Ba, K, HFSE, and other incompatible elements. The infiltration of the metasomatizing liquid occurred through interstices and vulnerable zones of enstatite grains and manifested in the crystallization of titanate inclusions. It is assumed that Cr-spinel lamellae served as seeds for their nucleation and growth. The prominent textural and chemical inhomogeneity of the interstitial oxide intergrowths is either a consequence of the metasomatic oxide crystallization shortly prior to the kimberlite magma eruption or arose from the intensive modification of preexisting oxide clusters by the kimberlite melt during the Udachnaya emplacement. Our new data provide implications for the metasomatic treatment of orthopyroxenites in the subcontinental lithospheric mantle from the view of exotic titanate occurrences.

We report the first natural occurrence and single-crystal X‑ray diffraction study of the Fe-analog of wadsleyite [ a = 5.7485(4), b = 11.5761(9), c = 8.3630(7) Å, V = 556.52(7) Å 3 ; space group Imma ], spinelloid-structured Fe 2 SiO 4 , a missing phase among the predicted high-pressure polymorphs of ferroan olivine, with the composition(Fe1.102+Mg0.80Cr0.043+Mn0.022+Ca0.02Αl0.02Na0.01)Σ2.01(Si0.97Αl0.03)Σ1.00O4.${{\left( \text{Fe}_{1.10}^{2+}\text{M}{{\text{g}}_{0.80}}\text{Cr}_{0.04}^{3+}\text{Mn}_{0.02}^{2+}\text{C}{{\text{a}}_{\text{0}\text{.02}}}\text{A}{{\text{l}}_{\text{0}\text{.02}}}\text{N}{{\text{a}}_{\text{0}\text{.01}}} \right)}_{\Sigma 2.01}}{{\left( \text{S}{{\text{i}}_{\text{0}\text{.97}}}\text{A}{{\text{l}}_{\text{0}\text{.03}}} \right)}_{\Sigma 1.00}}{{\text{O}}_{\text{4}}}.$ The new mineral was approved by the International Mineralogical Association (No. 2018-102) and named asimowite in honor of Paul D. Asimow, the Eleanor and John R. McMillan Professor of Geology and Geochemistry at the California Institute of Technology. It was discovered in rare shock-melted silicate droplets embedded in Fe,Ni-metal in both the Suizhou L6 chondrite and the Quebrada Chimborazo (QC) 001 CB3.0 chondrite. Asimowite is rare, but the shock-melted silicate droplets are very frequent in both meteorites, and most of them contain Fe-rich wadsleyite (Fa 30–45 ). Although the existence of such Fe-rich wadsleyite in shock veins may be due to the kinetic reasons, new theoretical and experimental studies of the stability of (Fe,Mg) 2 SiO 4 at high temperature (>1800 K) and pressure are clearly needed. This may also have a significant impact on the temperature and chemical estimates of the mantle’s transition zone in Earth.

In this issue This New Mineral Names has entries for 11 new minerals, including ammoniovoltaite, belousovite, chlorellestadite, clino-suenoite, marcobaldiite, markeyite, martinandresite, parisite-(La), plumbopharmacosiderite, somersetite, and ziminaite.