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The Mount Grace metamorphosed carbonatites (Late Devonian) outcrop as thin (0.5–4 m), laterally discontinuous, strata-bound mappable lenses within the Monashee complex of the southeastern Canadian Cordillera. The host stratigraphic sequence (Monashee cover gneiss) was metamorphosed and deformed in the Late Cretaceous to early Eocene followed immediately by exhumation of the Frenchman Cap and Thor Odin domes. We present seven stratigraphic logs for Mount Grace carbonatites including new and previously described outcroppings spanning ∼30 km. The Mount Grace carbonatite units were deposited regionally within or near the top of a shallow marine sedimentary sequence within miogeoclinal strata of the western margin of paleo-North America (Laurentia). The distribution of the Mount Grace carbonatite lithofacies and the preserved depositional structures and textures suggest that these are pyroclastic deposits resulting from phreatomagmatic eruptions. Our new data enhance the volcanological story with an eruption scenario involving phreatomagmatic reactions and deposition from pyroclastic density currents, sourced from multiple centers within a field of monogenetic maar volcanoes. The distribution of the Mount Grace carbonatites parallel to the western margin of the paleo-North American continent correlates well with regional Late Devonian alkaline magmatism associated with development of an extensional back-arc basin. [ABSTRACT FROM AUTHOR]

Cobalt-blue spinel from two localities (Qila and Trailside) on Baffin Island, Nunavut, Canada, are compared with other spinels from 12 occurrences in the same geological terrane and to Co-bearing blue spinel from other localities worldwide. Qila spinel is suitable for cutting cabochons, which commonly incorporate small amounts of associated calcite, dolomite, corundum, fluorapatite, pargasite and other silicates, as well as secondary cobaltpentlandite and fluid inclusions. Trailside spinel can be faceted into small gemstones (generally <0.2 ct), which rarely contain magnesite, fluorapatite, muscovite and CO2-rich fluid inclusions. The bright blue colour of the spinels from Qila and Trailside is due to TCo2+, although they also contain other chromophoric elements such as Fe and traces of Cr, Mn and V. Compared with other Mg-Al spinels from Baffin Island, those from Qila and Trailside are generally enriched in Co, Ni, Mn, Li and Be, and depleted in Ti, V and Cr. In addition, the Qila and Trailside Co-blue spinels are fairly chemically distinct from those of other world localities: they are depleted in V and Ti, fairly poor in Cr and Zn, and considerably enriched in Co and Mn. A new approach for the preliminary chemical discrimination of gem spinels is proposed by plotting the weighted chromophore concentrations in a ternary diagram (i.e. Cr+V vs 40×Co vs Fe/8). These weighted percentage values are also plotted against the ppmw concentrations of the chromophoric elements in X-Y plots, which provide further correlations of high Co with vivid Co-blue spinel and elevated Fe with overly dark non-gem spinel. This method can be applied to samples that are difficult or inefficient to characterise using spectroscopy, such as spinel grains in heavy-mineral concentrates obtained during regional exploration programmes. [ABSTRACT FROM AUTHOR]

The sparkle and luster of gemstones has made them prized objects for thousands of years. Gems are valued for their color, luster, transparency, durability and high value-to-volume ratio. Because many [...]

Joelbruggerite, ideally [Pb.sub.3][Zn.sub.3]([Sb.sup.5+], [Te.sup.6+])[As.sub.2][O.sub,13](OH,O), is a new arsenate mineral (IMA2008-034) and the [Sb.sup.5+] analog of dugganite, from the Black Pine mine, 14.5 km northwest of Philipsburg, Granite County, Montana. It is usually found perched on mimetite; other species that may be present include malachite, azurite, pseudomalachite, chalcocite, beudantite-corkite, duftite, dugganite, and kuksite, in milky quartz veins. Joelbruggerite occurs as barrel-shaped or prismatic crystals up to about 50 [micro]m across in various shades of purple. The crystals have an adamantine luster and a white streak. Mohs hardness is about 3. The fracture is irregular, and the tenacity is brittle. Joelbruggerite crystals are uniaxial (-), with a calculated refractive index of n = 1.993, and weakly pleochroic: X Y = gray, Z = purple; absorption: Z > X = Y. Crystals show straight extinction and are length-fast. The empirical chemical formula (mean of 5 electron microprobe analyses) calculated on the basis of 14 [O + OH] anions is [[Pb.sub.3.112]([Zn.sub.2.689][Fe.sup.2+.sub.0.185]).sub.[SIGMA]2.874] [([Sb.sup.5+.sub.0.650][Te.sup.6+.sub.0.451].sub.[SIGMA]1.101] [([As.sub.1.551][P.sub.0.203][Si.sub.0.160].sub.[SIGMA]1.914] [O.sub.13.335[(OH).sub.0.665]. Joelbruggerite is trigonal, space group P321, a = 8.4803(17),c 5.2334(12) [Angstrom], V= 325.94(12) [[Angstrom].sup.3], Z = 1. The five strongest lines in the powder X-ray diffraction pattern are [[d.sub.obs] in [Angstrom] (I) (hk/)]: 3.298 (100) ( 111 ), 3.008 (89) (021), 1.905 (39) (122, 131), 2.456 (36) (012, 121,030), and 1.609 (30) (112, 132, 231, 140). The crystal structure was solved from single-crystal X-ray diffraction data and refined to [R.sub.1] = 0.038 on the basis of 604 unique reflections with F > 4[sigma](F). It is composed of heteropolyhedral sheets of edge-sharing (Sb,Te)[O.sub.6] octahedra and Pb[O.sub.8] disphenoids, oriented parallel to (001). The sheets are cross-linked by As[O.sub.4] and Zn[O.sub.4] tetrahedra, which share comers to form an interlinked, two- and three- connected two-dimensional net parallel to (001). The mineral is named for JoEl Brugger (born 1967), Swiss-Australian mineralogist, for his contributions to mineralogy. Keywords: Joelbruggerite, new mineral, [Sb.sup.5+], arsenate, Black Pine mine, dugganite, crystal structure, bond valence

The famous amethyst geodes of Brazil and Uruguay rarely contain crystals of 'skunk' calcite, wherein microcrystals of goethite form sharp, narrow black bands on rhombohedral calcite faces. Close study reveals [...]

We report on temperature dependencies of infrared (IR) fundamental, combination, and overtone vibrations of hydroxyl species (OH) in nominally anhydrous minerals (e.g., titanite), ferroelectric crystals (K[Ta.sub.1] [sub.x][Nb.sub.x][O.sub.3], KTN), layer silicates (talc, mica, and pyrophyllite), and hydrous minerals such as apatite and synthetic hydrous/deuterated garnets [[Ca.sub.3][A1.sub.2][([O.sub.4][H.sub.4]).sub.3] and [Ca.sub.3][Al.sub.2][([O.sub.4][D.sub.4]).sub.3]] for the temperature range of 20-300 K. Data obtained by high- resolution FTIR spectroscopy show that increasing temperature generally leads to a decrease in the band height and band area of fundamental vibrations of hydroxyl species, whereas the combination and first-overtone bands commonly show different temperature dependencies. The results show that in the investigated temperature range, the variations of the band height and area for different OH bands (especially for combinations and overtones) on cooling or heating do not reflect changes in OH concentrations in the materials, but relate to temperature-dependent absorption coefficients. The observations imply that absorption coefficients calibrated at room temperature cannot necessarily be used for the determination of hydroxyl contents at other temperatures. Keywords: Infrared spectroscopy, low temperature, apatite, hydrous garnet, pyrophyllite, tale, sericite, titanite

The electron microprobe compositions and crystal structure of seven members of the grandidierite-ominelite (Mg[Al.sub.3]BSi[O.sub.9-[Fe.sup.2+][Al.sub.3]BSi[O.sub.9]) series with X = ([Fe.sup.2+] + Mn + Zn)/([Fe.sup.2+] + Mn + Zn + Mg) ranging from 0.00 to 0.52 were studied to determine the geometric effects of Fe substitution for Mg on the crystal structures. Calculating [Fe.sup.3+] from the electron microprobe analyses gave 0.04-0.06 [Fe.sup.3+] apfu, but such small amounts at the Al sites could not be detected in the refinements. Regression equations derived from single-crystal X-ray diffraction data show that b increases by 0.18 [Angstrom] from X=0-1. The crystal structure refinements show that the most significant changes involve the (Mg,[Fe.sup.2+])[O.sub.5] polyhedron, which increases in volume by 0.36 [[Angstrom].sup.3] (5.0%), largely as a result of expansion of the MgFe05, -O2, and -O6 (x2) bond distances, which increase by 0.09 (4.4%), 0.06, and 0.04 [Angstrom], respectively. Other significant changes include increasing Ol-MgFe-O2 (3.44[degrees]) and -A13-O5a angles (1.9[degrees]) and a decreasing O6-MgFe-O6b (-2.20[degrees]) angle. Significant increases ate also seen in the lengths of the O1-O2 (0.13 [Angstrom]) and O6-O5a (x2) (0.09 [Angstrom]) edges. The Si[O.sub.4] tetrahedra appear to respond to changes in the surrounding polyhedra by changing O-Si-O angles such that the tetrahedral angle variance and mean tetrahedral quadratic elongation increase with X. The B[O.sub.3] triangles appear to behave as relatively invariant units in the crystal structure. Regression equations obtained from the MgFe-O bond distances were used to determine a radius for [sup.v][Fe.sup.2+] of 0.70 [Angstrom]. Although our samples show little Mn, the presence of [Mn.sup.2+] at the MgFe site would be expected to cause more distortion than an equivalent amount of [Fe.sup.2+]. Substitution of Zn likely would have little effect. The presence of [Cr.sup.3+] at any of the Al sites would be expected to increase the size of the coordination sphere, but the substitution of [p.sup.5+] for Si at the Si sites would most likely decrease the Si-O bond distances. Keywords: Grandidierite, ominelite, crystal structure, substitution, borosilicates

SUMMARY This paper reviews the geology, mineralogy, and origin of the gem varieties of beryl, including emerald (green) and aquamarine (blue); it focuses on western Canada, especially the Yukon Territory, [...]

The influence of F substitution on the local structure of Al in the tetrahedral and octahedral sheets of synthetic Al-rich phlogopite samples with nominal gel compositions of K([Mg.sub.3-x][Al.sub.x] [[Al.sub.1+x][Si.sub.3-x][O.sub.10]] [(OH).sub.y][(F).sub.2-y] between 0.0 [less than or equal to] x [less than or equal to] 0.8 and 0.5 [less than or equal to] y [less than or equal to] 1.8, was studied by [sup.27]Al MAS, MQMAS, {[sup.1]H/[sup.19]F} [vector] [sup.27]Al 2D CPMAS (HETCOR) and {[sup.1]H/[sup.19]F} [sup.27]Al REDOR solid-state NMR an by IR spectroscopy. Changes in intensity of the absorption bands in the OH-stretching region of the IR spectra clearly indicate the incorporation of octahedral Al. Signais from the different phases can be separated in the [sup.27]Al MQMAS NMR spectra by generation of an isotropic dimension in F1. The [sup.27]Al quadrupolar parameters of the four phases were estimated from [sup.27]Al MAS NMR spectra obtained at 104.26 and 208.42 MHz. The quadrupolar coupling constant and isotropic chemical shift increases with increasing Al content for the [sup.IV]Al site in phlogopite. The [sup.VI]Al site shows a clear increase of the asymmetry parameter and [C.sub.Q] with increasing F content. The estimated [sup.27]Al signal areas show the lowest amount of impurity phases at high OH contents and a stabilization of [sup.VI]Al sites by hydroxyl groups. The {[sup.1]H} [vector] [sup.27]Al 2D CPMAS (HETCOR) NMR experiment at short contact rimes provides information about site neighborhoods of tetrahedral Al sites and [Mg.sub.3]OH as well as [Mg.sub.2]AlOH sites, whereas magnetization is only transferred to the octahedral Al sites from hydroxyl groups in [Mg.sub.2]AlOH sites. The {[sup.1]H/[sup.19]F} [vector] [sup.27]Al 2D CPMAS (HETCOR) NMR spectrum is dominated by [sup.IV]Al sites coupled to the [Mg.sub.3]F complex in phlogopite. Resonances from [Mg.sub.2]AlF complexes are not observed. Finally, the {[sup.1]H/[sup.19]F} [sup.27]Al REDOR experiments support the results of the 2D CPMAS (HETCOR) experiments.

The amblygonite-montebrasite series of minerals, common constituents of granitic pegmatites and topaz-bearing granites, show complete solid solution with ideal composition LiAlP[O.sub.4](F, OH). These compounds are ideal for studying F [left and right arrow] OH solid solution in minerals because natural members of the series generally show little deviation from the ideal composition. In this study, we used powder and single-crystal neutron diffraction and solid-state [sup.6]Li MAS, CP MAS, and REDOR NMR techniques to study the effect of F [left and right arrow] OH substitution on the series. Lattice parameters refined from single-crystal neutron diffraction data show increasing b and decreasing a, c, and V with increasing F/(F + OH). The volume is highest for the OH end-member because of the presence of an additional atom (H). The a and c parameters decrease with increasing F/(F + OH) because the O-H vector is close to the a-c plane and the Al-OH/F vectors are approximately parallel to c. Lattice parameters refined from neutron powder diffraction patterns collected at lower T show that thermal contraction increases with F/(F + OH), presumably because the F anion takes up less space than the OH molecule. The results show that the OH/F position is always fully occupied. The H displacement ellipsoid shows little change with occupancy, which obviously corresponds negatively with increasing F/(F + OH). However, the Li displacement ellipsoid becomes extremely large and anisotropic with increasing F fraction. Most of the distortion is associated with the [U.sub.3] eigenvalue, which lies between the c and c* directions. [U.sub.eq] values corresponding to the Li atom show a greater reduction with decreasing temperature than the other atoms. The temperature dependence of Li is the same regardless of F content. Even when extrapolated to absolute zero the Li displacement ellipsoid is very large, which implies a large static disorder. At the montebrasite end of the series, there are five short Li-[phi] ([phi] = O, OH, F) distances and one very long Li-O4 bond. With increasing F content, the Li-O4 distance decreases and the Li-O3f distance increases, such that at the amblygonite end, the coordination is 4 + 2. The disorder in the Li site is obviously caused by the substitution of F for OH. The driving force is the loss of the hydrogen bond to 04, which causes the Li-O4 bond to strengthen and improves the bond valence to 04. The results show that the H atom position is imbedded within the distorted octahedral oxygen coordination of the Li atom. To represent the disorder better, we used a split Li site model. The results show that Li1 occupancy increases and the Li2 occupancy decreases with increasing F content, and that the Li1-Li2 distance is longer for intermediate compositions than for the end-members. The [sup.6]Li MAS NMR experiments provide important structural information complementary to the neutron diffraction results. The spectra of samples in the amblygonite-montebrasite series show two well-resolved peaks, confirming the presence of Li disorder over two distinct sites, and highly resolved [sup.6]Li MAS NMR spectra are obtained at the very high magnetic field strength of 18.8 T. The peaks at -0.3 ppm and -0.9 ppm were unambiguously assigned to the Li2(OH) and Li1(F) sites found in the neutron diffraction structures. The isotropic chemical shifts are consistent with the coordinations of these Li sites found in the neutron diffraction structures. The relative intensities of the two peaks across the series of samples reflect the varying F/(F + OH). In addition to confirming the assignments of the peaks, it is possible to measure H-Li2 and F-Li1 internuclear distances by [sup.6]Li{[sup.1]H} and [sup.6]Li {[sup.19]F} CP and REDOR NMR that are consistent with the corresponding distances from the neutron diffraction structures. The [sup.6]Li{[sup.1]H} and [sup.6]Li{[sup.19]F} CP and REDOR results indicate that the Li disorder is random throughout the crystals rather than over large domains, a conclusion that cannot be made from diffraction experiments. Variable temperature [sup.6]Li MAS NMR spectra confirm that the disorder is static and there is no dynamic exchange involving F, OH, or Li. Each Li ion has access to only one of the two observed sites as determined by the presence of either OH or F in its immediate environment and there is no possibility of a dynamic exchange.

The influence of F content on the formation and stability of Al-rich phlogopite has been investigated. Samples with varying OH/F-ratios and nominal gel compositions of K([Mg.sub.3-x][Al.sub.x])([Al.sub.1+x][Si.sub.3 -x][O.sub.10])[(OH).sub.y] [(F).sub.2-y] (0.0 [less than or equal to] x [less than or equal to] 0.8 and 0.5 [less than or equal to] y [less than or equal to] 1.8) were studied using [sup.29]Si, [sup.1]H, and [sup.19]F MAS NMR spectroscopies, powder X-ray diffraction, electron-probe microanalysis, and scanning electron microscopy. The synthetic phlogopites were synthesized from sol-gels in cold-seal pressure vessels at 1073 K, 2 kbar. The main phase (phlogopite) and three other impurity phases [corundum ([alpha]-[Al.sub.2][O.sub.3]), kalsilite (KalSi[O.sub.4]), and potassium aluminum hexafluoride ([K.sub.3]Al[F.sub.6]*0.5[H.sub.2]O)] were clearly identified by powder X-ray diffraction and electron-probe microanalysis. For phlogopite, the unit-cell parameters [a.sub.0] and [b.sub.0] decrease whereas [c.sub.0] increases with increasing Al-content (x). The average crystal size of phlogopite is about 1-2 [micro]m. The [sup.29]Si MAS NMR spectra show up to four resonances at approximately -91, -87, -83, and -80 ppm, which can be assigned as [Q.sup.3](n Al) signals with n = 0-3. The ideal [Si/.sup.IV] Al ratio calculated from the initial composition is always lower than that derived experimentally. Hydroxyl-rich compositions indicate an increased Al-content in the tetrahedral sheets, suggesting a stabilizing effect on the formation of Al-rich phlogopite. These conclusions are supported by [sup.1]H and [sup.19]F MAS NMR spectra. The [sup.1]H MAS NMR spectra show a water signal at 4.7 ppm, a signal due to [Mg.sub.2]AlOH at 1.8 ppm, and a signal due to [Mg.sub.3]OH at 0.7 ppm. The [sup.19]F MAS NMR spectra exhibit a signal for [Mg.sub.2]AlF at -150 ppm, one due to Al[F.sub.6] ([K.sub.3]Al[F.sub.6]*0.5[H.sub.2]O) at -157 ppm, and one for [Mg.sub.3]F at -174 ppm. Comparison of the [sup.1]H and [sub.19]F MAS NMR spectra for different Al- and F-contents reveals a non-statistical distribution of F- and OH-groups at the crystallographic sites in the octahedral sheets where F prefers sites coordinated by three Mg, and OH sites with Al in the next-nearest coordination sphere.

Radiation damage and the recrystallization of natural titanite (CaTiSi[O.sub.5]) were studied using infrared spectroscopy in the spectral range from 50 to 7500 [cm.sup.-1]. The results show that radiation damage leads to systematic changes in spectral features: decreasing absorption and reflectivity, line broadening, and loss of orientational dependence. Strongly damaged titanite shows hydroxylate bands between 2200 and 3500 cm-j. The band most affected by radiation damage is the Ti-O stretching band near 670 [cm.sup.-1]. It shifts to 710 [cm.sup.-1] in the most damaged samples, possibly indicating the presence of Ti[O.sub.5] complexes in metamict titanite. Titanite glasses (quenched melts of CaTiSi[O.sub.5]) show spectral features different from those of radiation-damaged titanite, especially in the Ti-O and Si-O stretching regions. Annealing radiation-damaged titanites at high temperatures results in the recovery of damaged crystalline regions. Recrystallization near 900 K is characterized by an increase in reflectivity, integrated absorbance, and line sharpening. Different infrared bands show recovery at different temperatures. The restoration of the Ti-O stretching band near 670 [cm.sup.-1] and an infrared band near 285 [cm.sup.-1] took place at temperatures of 1200-1400 K. Temperature-induced changes of the OH-absorption bands could be responsible for the previously reported differences in the temperature evolution of infrared spectra of OH species between in situ and quench experiments.

Celleriite, □ ( Mn 2 2 + Al) Al 6 ( Si 6 O 18 ) ( BO 3) 3 (OH) 3 (OH) , $\square \,\left(\text{Mn}_{2}^{2+}\text{Al} \right)\text{A}{{\text{l}}_{6}}\left(\text{S}{{\text{i}}_{6}}{{\text{O}}_{18}} \right){{\left(\text{B}{{\text{O}}_{3}} \right)}_{3}}{{(\text{OH})}_{3}}(\text{OH}),$ is a new mineral of the tourmaline supergroup. It was discovered in the Rosina pegmatite, San Piero in Campo, Elba Island, Italy (holotype specimen), and in the Pikárec pegmatite, western Moravia, Czech Republic (co-type specimen). Celleriite in hand specimen is violet to gray-blue (holotype) and dark brownish-green (co-type) with a vitreous luster, conchoidal fracture, and white streak. Celleriite has a Mohs hardness of ~7 and a calculated density of 3.13 and 3.14 g/cm3 for holotype and its co-type, respectively. In plane-polarized light in thin section, celleriite is pleochroic (O = pale violet and E = light gray-blue in holotype; O = pale green and E = colorless in co-type) and uniaxial negative. Celleriite has trigonal symmetry: space group R3m, Z = 3, a = 15.9518(4) and 15.9332(3) Å, c = 7.1579(2) and 7.13086(15) Å, V = 1577.38(9) and 1567.76(6) Å3 for holotype and co-type, respectively (data from single-crystal X‑ray diffraction). The crystal structure of the holotype specimen was refined to R1 = 2.89% using 1696 unique reflections collected with MoKα X‑ray intensity data. Structural, chemical, and spectroscopic analyses resulted in the formulas: x (□ 0.58 Na 0.42 ) ∑ 1.00 Y ( Mn 1.39 2 + Fe 0.16 2 + Mg 0.01 Al 1.14 Fe 0.01 3.0 Li 0.28 T 0.01 ) Σ 3.00 Z Al 6 [ T ( Si 5.99 Al 0.01 ) Σ 6.00 O 18 ] ( BO 3) 3 (OH) 3 w [ (OH) 0.65 F 0.03 O 0.32 ] Σ 1.00 (for holotype) $\begin{align}& \,\,\,\,{{\,}^{\text{x}}}{{\left({{\square }_{0.58}}\text{N}{{\text{a}}_{0.42}} \right)}_{\sum 1.00}}\text{Y}{{\left(\text{Mn}_{1.39}^{2+}\text{Fe}_{0.16}^{2+}\text{M}{{\text{g}}_{0.01}}\text{A}{{\text{l}}_{1.14}}\text{Fe}_{0.01}^{3.0}\text{L}{{\text{i}}_{0.28}}~{{\text{T}}_{0.01}} \right)}_{\Sigma 3.00}}^{\text{Z}}\text{A}{{\text{l}}_{6}}\left[ {{~}^{\text{T}}}{{\left(\text{S}{{\text{i}}_{5.99}}\text{A}{{\text{l}}_{0.01}} \right)}_{\Sigma 6.00}}{{\text{O}}_{18}} \right]{{\left(\text{B}{{\text{O}}_{3}} \right)}_{3}}{{(\text{OH})}_{3}} \\ & ^{\text{w}}{{\left[ {{(\text{OH})}_{0.65}}~{{\text{F}}_{0.03}}{{\text{O}}_{0.32}} \right]}_{\Sigma 1.00}}\,\text{(for}\,\text{holotype)} \\ \end{align}$ and X (□ 0.51 Na 0.49 ) Σ 1.00 Y ( Mn 0.90 2 + Fe 050 2 + Al 1.36 Fe 004 3 + Li 0.17 Zn 0.04 ) Σ 3.00 Z Al 6 [ T ( Si 5.75 B 0.25 ) Σ 6.00 O 18 ] ( BO 3) 3 (OH) 3 w [ (OH) 0.35 F 0.17 O 0.48 ] ∑ 1.00 (for co-type) $\begin{align}& \,\,\,\,\,{{\,}^{\text{X}}}{{\left({{\square }_{0.51}}\text{N}{{\text{a}}_{0.49}} \right)}_{\Sigma 1.00}}^{\text{Y}}{{\left(\text{Mn}_{0.90}^{2+}\text{Fe}_{050}^{2+}\text{A}{{\text{l}}_{1.36}}\text{Fe}_{004}^{3+}\text{L}{{\text{i}}_{0.17}}\text{Z}{{\text{n}}_{0.04}} \right)}_{\Sigma 3.00}}^{\text{Z}}\text{A}{{\text{l}}_{6}}\left[ ^{\text{T}}{{\left(\text{S}{{\text{i}}_{5.75}}~{{\text{B}}_{0.25}} \right)}_{\Sigma 6.00}}{{\text{O}}_{18}} \right]{{\left(\text{B}{{\text{O}}_{3}} \right)}_{3}}{{(\text{OH})}_{3}} \\ & ^{\text{w}}{{\left[ {{(\text{OH})}_{0.35}}~{{\text{F}}_{0.17}}{{\text{O}}_{0.48}} \right]}_{\sum 1.00}}\text{(for}\,\text{co-type)} \\ \end{align}$ Celleriite is a hydroxy species belonging to the X-site vacant group of the tourmaline supergroup. The new mineral was approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, proposal no. 2019-089. In the Rosina pegmatite, celleriite formed an overgrowth at the analogous pole of elbaite–fluorelbaite–rossmanite crystals during the latest stage of evolution of pegmatite cavities after an event of a pocket rupture. In the Pikárec pegmatite, celleriite occurs as an intermediate growth sector of elbaite, princivalleite, and fluor-elbaite. [ABSTRACT FROM AUTHOR]

Interpretation of various exploration data, in particular geochemical prospecting, offers a powerful and rapid assessment of grass‐root projects in a green‐field terrain. Here, we present an example of the Collins epithermal prospect in Aceh Province, Indonesia. In this area, the Au+ base‐metal‐bearing sheeted quartz veins (individually mostly 2–4 cm wide), which are controlled by a 250 m wide by 800 m long NNE‐trending structural corridor within Paleogene sandstone and volcanic rocks, are the product of two main stages of deposition. Stage I formed veins with a sliver of cryptocrystalline quartz wall zone followed by an inner zone of comb quartz with interstitial rhombic adularia that terminates in open space. Stage I or main‐stage sulfide mineralization consisting of early galena + sphalerite and later chalcopyrite occurs with the quartz + adularia. Small amounts of galena also occur in the wall zone. Stage II mineralization brecciated Stage I veins and overprinted them with silicification characterized by vuggy texture. Mineralization associated with this episode consists of earlier chalcopyrite + sphalerite + tennantite–tetrahedrite and later, vug‐filling Au–Ag alloy (Ag0.37–0.41Au0.62–0.59). The above mineralized veins are successively flanked by silicic selvages, an illite + chlorite + pyrite ± kaolinite zone and a chlorite + epidote + carbonate + pyrite zone. Local supergene alteration induced replacement of galena by plumbogummite and anglesite and chalcopyrite by covellite. Data from fluid inclusion microthermometry in quartz indicated that the inner zone of Stage I veins formed from fluids with a 2.3 wt% salinity (0.5–3.3 wt% NaCl equivalent), at 174°C (155–211°C). Combining these physico‐chemical parameters with the mineral assemblage, the mineralization occurred under a reduced environment. Rock and soil assays indicate that elevated Au concentrations (up to 16.5 ppm over 1 m) occur along northeast‐trending zones and show a strong correlation with Pb, while Cu (up to 2.58% over 1 m), Zn, As, Sb, and Mo anomalies lie mostly at the periphery. The high‐grade mineralized veins correlate with moderate to high resistivity and chargeability zones, and the pseudosections of such geophysical signals are interpreted as reflecting coalesced or enlarged veins at depth, or inclined veins in other localities. The intermediate sulfidation affinity for Collins points to potential mineralization at depth as well as preservation of Au‐rich and sulfide‐poor zones in the less eroded areas. [ABSTRACT FROM AUTHOR]

The Silvana mine has produced an array of very fine to spectacular micromineral and thumbnail specimens including rare, fiery-orange pyrostilpnite, lustrous cubanite, pyrargyrite and stephanite as well as showy, irridescent [...]

The Engineer mine is a Dana locality for classic, botryoidal 'allemontite' (stibarsen and native arsenic). Several other minerals of interest to the collector are also found, including crystallized auriferous silver [...]

Synchrotron radiation, high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction, and Raman spectroscopy were used to study the structure and thermal behavior of malayaite, CaSnSi[O.sub.5]. No indications of deviation from A2/a symmetry and no structural transitions were observed between 100 and 870 K. HRTEM revealed that the material is free of domains and antiphase boundaries. However, the lattice constants, cell volume, and Raman-active phonons show a thermal discontinuity near 500 K, which is possibly related to variation of the coordination sphere around the highly anisotropic Ca position.