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Eddavidite is a new mineral species (IMA2018-010) with ideal formula, Cu12Pb2O15Br2, and cubic Fm 3 ¯ m symmetry: a = 9.2407(9) Å; V = 789.1(2) Å3; Z = 2. Eddavidite is the bromine analog of murdochite, Cu12Pb2O15Cl2, with which it forms a solid solution series. The type locality is the Southwest mine, Bisbee, Cochise County, Arizona, U.S.A. Eddavidite also occurs in the Ojuela mine, Mapimí, Durango, Mexico. Eddavidite occurs as domains within mixed murdochite–eddavidite crystals. The empirical formula, normalized to 12 Cu apfu, is Cu12(Pb1.92Fe0.06Si0.06)(O15.08F0.02)-(Br0.99Cl0.89☐0.12). Type locality samples contain up to 67% eddavidite component, while Ojuela mine samples contain up to 62%. Mixed eddavidite–murdochite crystals show forms {100} and {111}; the habit grades from cubic through cuboctahedral to octahedral. Mixed eddavidite–-murdochite crystals exhibit good cleavage on {111}. Eddavidite is black, opaque with submetallic luster, and visually indistinguishable from intergrown murdochite. Its Mohs hardness is 4; dmeas. = 6.33 g/cm3, dcalc. = 6.45 g/cm3. The crystal structure, refined to R = 0.0112, consists of corner-sharing square planar CuO4 units, arranged in Cu12O24 metal oxide clusters, which encapsulate Br atoms. PbO8 cubes share edges with Cu12O24 clusters in a continuous framework. Eddavidite incorporates bromine remaining after desiccation of paleo-seawater at its two known localities, which were both once situated along the Western Interior Seaway. [ABSTRACT FROM AUTHOR]

ABSTRACT Stibioclaudetite is a new mineral species with ideal chemistry [AsSbO.sub.3]. The mineral has monoclinic symmetry, [P2.sub.1]/n, with a = 4.5757(4) Å, b = 13.1288(13) Å, c = 5.4216(5) Å, [...]

Outstanding azurite crystals and malachite pseudomorphs from the Milpillas copper mine began appearing on the mineral market in 2006. At their best, these specimens compare well with classics from Bisbee [...]

California collector Hubert de Monmonier built a remarkable mineral collection of over 800 specimens, heavy in native gold and amethyst, and valued at over $7 million. In accordance with his [...]

Wulfenite appears to be quite rare in China. Until recently, only a few mediocre specimens with small yellow to red crystals have reached the specimen market, from a rare-earth mine [...]

The crystal structure of synthetic kosmochlor, NaCr[Si.sub.2][O.sub.6], was studied using single crystal X-ray diffraction at high pressure. A four-pin diamond anvil cell, with 4:1 methanol:ethanol pressure medium, was used to achieve pressures to 9.28 GPa. Unit-cell data were collected at 20 pressures, and intensity data were collected at 13 of these pressures. Fitting the P-V data to a third-order Birch-Murnaghan equation yields [V.sub.0] = 418.84(3) [Angstrom]3, [K.sub.0] = 134(1) [GPa.sup.-1], and [K'.sub.0] = 2.0(3). Anisotropic compression was observed with unit strain axial ratios of 1:1.82:2.08. The Cr[O.sub.6] octahedron has a bulk modulus [K.sub.0] = 90(16) [GPa.sub.-1], while the Si[O.sub.4] tetrahedron has [K.sub.0] = 313(55) [GPa.sup.-1], both with [K'.sub.0] [equivalent to] 4. An o-type rotation of the O3-O3-O3 linkage was observed with pressure, with [angle] O3-O3-O3 decreasing from 172.8(2)[degrees] to 166.1(7)[degrees]. Compression in kosmochlor is related to the stacking directions of distorted cubic closest packed O atom monolayers. Unit strain ellipsoids for diopside, hedenbergite, spodumene (C2/c and [P2.sub.1]/c), LiSc[Si.sub.2][O.sub.6] (C2/c and [P2.sub.1]/c), clinoenstatite, orthoenstatite, and [Mg.sub.1.54] [Li.sub..23][Sc.sub..23][Si.sub.2][O.sub.6] (Pbcn and [P2.sub.1]cn) were generated and discussed in terms of closest packing systematics. A relationship between the anisotropy of compression of olivines and pyroxenes is established. A strategy to determine not only the direction of a stress field in deformed rocks, but also an estimate of the magnitude of stress is discussed in terms of comparing the anisotropy of olivine and pyroxene.

INTRODUCTION During the Denver mineral show of 2005, the senior author noticed a specimen of stibnite with red and yellow encrustations, identified as 'cetineite' and 'cervantite,' respectively. The specimen owner, [...]

The 'Anthropocene Epoch' has been proposed as a new post-Holocene geological time interval-a period characterized by the pervasive impact of human activities on the geological record. Prior to the influence of human technologies, the diversity and distribution of minerals at or near Earth's surface arose through physical, chemical, and/or biological processes. Since the advent of human mining and manufacturing, particularly since the industrial revolution of the mid-eighteenth century, mineral-like compounds have experienced a punctuation event in diversity and distribution owing to the pervasive impact of human activities. We catalog 208 mineral species approved by the International Mineralogical Association that occur principally or exclusively as a consequence of human processes. At least three types of human activities have affected the diversity and distribution of minerals and mineral-like compounds in ways that might be reflected in the worldwide stratigraphic record. The most obvious influence is the widespread occurrence of synthetic mineral-like compounds, some of which are manufactured directly for applications (e.g., YAG crystals for lasers; Portland cement) and others that arise indirectly (e.g., alteration of mine tunnel walls; weathering products of mine dumps and slag). A second human influence on the distribution of Earth's near-surface minerals relates to large-scale movements of rocks and sediments-sites where large volumes of rocks and minerals have been removed. Finally, humans have become relentlessly efficient in redistributing select natural minerals, such as gemstones and fine mineral specimens, across the globe. All three influences are likely to be preserved as distinctive stratigraphic markers far into the future. [ABSTRACT FROM AUTHOR]

The crystal structure of ruizite, ideally Ca2Mn3+2[Si4O11(OH)2](OH)2?2H2O [dicalcium dimanganese(III) tetrasilicate tetrahydroxide dihydrate] was first determined in space group A2 with an isotropic displacement parameter model (R = 5.6%) [Hawthorne (1984). Tschermaks Mineral. Petrogr. Mitt. 33, 135-146]. A subsequent refinement in space group C2/m with anisotropic displacement parameters for non-H atoms converged with R = 8.4% [Moore et al. (1985). Am. Mineral. 70, 171-181]. The current study reports a redetermination of the ruizite structure by means of single-crystal X-ray diffraction data of a natural sample from the Wessels mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Our data (R1 = 3.0%) confirm that the space group of ruizite is that of the first study rather than C2/m. This work improves upon the structure reported by Hawthorne (1984) in that all non-H atoms were refined with anisotropic displacement parameters and all hydrogen atoms were located. The crystal structure consists of [010] chains of edge-sharing MnO6 octahedra flanked by finite [Si4O11(OH)2] chains. The Ca2+ cations are situated in the cavities of this arrangement and exhibit a coordination number of seven. [ABSTRACT FROM AUTHOR]

Bartelkeite from Tsumeb, Namibia, was originally described by Keller et al. (1981) with the chemical formula PbFeGe3O8. By means of electron microprobe analysis, single-crystal X-ray diffraction, and Raman spectroscopy, we examined this mineral from the type locality. Our results show that bartelkeite is monoclinic with space group P21/m, unit-cell parameters a = 5.8279(2), b = 13.6150(4), c = 6.3097(2) Å, β = 127.314(2)°, and a revised ideal chemical formula PbFeGeVIGe2IVO7(OH)2·H2O (Z = 2). Most remarkably, bartelkeite is isostructural with the high-pressure P21/m phase of lawsonite, CaAl2Si2O7(OH)·H2O, which is only stable above 8.6 GPa and a potential host for H2O in subducting slabs. Its structure consists of single chains of edge-sharing FeO6 and Ge1O6 octahedra parallel to the c-axis, cross-linked by Ge22O7 tetrahedral dimers. The average bond lengths for the GeO6 and GeO4 polyhedra are 1.889 and 1.744 Å, respectively. The Pb atoms and H2O groups occupy large cavities within the framework. The hydrogen bonding scheme in bartelkeite is similar to that in lawsonite. Bartelkeite represents the first known mineral containing both 4- and 6-coordinated Ge atoms and may serve as an excellent analog for further exploration of the temperature-pressure-composition space of lawsonite. [ABSTRACT FROM AUTHOR]

Single crystal XRD results reveal that the naturally occurring title mineral (Tsumeb, Otavi Mountains, Namibia) crystallizes in the hexagonal space group P63/mmc with Z = 2. [ABSTRACT FROM AUTHOR]

The article discusses the gemological properties of some fragments of a triploidite from China that were donated to the Gemological Institute of America (GIA) for examination. The samples exhibited very weak pleochroism, a refractive index of 1.660-1.679 and a spot reading of 1.66, a birefringence of 0.019, a hydrostatic specific gravity of 3.83 and 3.80 and a fluorescence of inert to long- and short-wave ultraviolet (UV) radiation. Microscopic examination revealed numerous two-phase inclusions and fractures.

Single crystal XRD of a twinned crystal of the title mineral (specimens from Pirquitas deposit, Jujuy Province, Argentina) shows anisotropic displacement parameters for all atoms and a measured composition of (Ag1.87Cu0.13) (Zn0.61Fe0.36Cd0.03)SnS4. [ABSTRACT FROM AUTHOR]