ALBERT

Description: Manganoquadratite, ideally AgMnAsS3, is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as dark gray, anhedral to subhedral grains up 0.5 mm across, closely associated with alabandite, Mn-rich calcite, Mn-rich sphalerite, proustite, pyrite, pyrrhotite, tennantite, argentotennantite, stannite, and other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S. Manganoquadratite is opaque with a metallic luster and possesses a reddish-brown streak. It is brittle, the Vickers microhardness (VHN10) is 81 kg/mm2 (range 75–96) (corresponding Mohs hardness of 2–2½). The calculated density is 4.680 g/cm3 (on the basis of the empirical formula). In plane-polarized reflected light, manganoquadratite is moderately bireflectant and very weakly pleochroic from dark gray to a blue gray. Internal reflections are absent. Between crossed polars, the mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) for the four standard COM wavelengths are 29.5, 31.8 (471.1 nm), 28.1, 30.5 (548.3 nm), 27.3, 29.3 (586.6 nm), and 26.0, 28.2 (652.3 nm), respectively.Manganoquadratite is tetragonal, space group P4322, with unit-cell parameters: a = 5.4496(5), c = 32.949(1) Å, V = 978.5(1) Å3, c:a = 6.046, Z = 8. The structure, refined to R1 = 0.0863 for 907 reflections with Fo 〉 4σ(Fo), consists of a stacking along [001] of alabandite-like Mn2S2 layers connected to each to other by a couple of AgAsS2 sheets where As3+ forms typical AsS3 groups, whereas Ag+ cations are fivefold coordinated. The six strongest lines in the observed X-ray powder-diffraction pattern [d in Å (I/I0) (hkl)] are: 3.14 (60) (116), 2.739 (50) (0 0 12), 2.710 (100) (200), 1.927(70) (2 0 12 + 220), 1.645 (25) (3 0 16), and 1.573 (20) (22 12).Electron microprobe analyses gave the chemical formula (on the basis of six atoms) (Ag0.95Cu0.05)∑=1.00 (Mn0.96Pb0.04)∑=1.00(As0.87Sb0.14)∑=1.01S2.99, leading to the simplified formula AgMnAsS3.The name was chosen to indicate the close analogy of the formula and unit-cell dimensions with quadratite, Ag(Cd,Pb)(As,Sb)S3. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA 2011-008.

Description: Menchettiite, ideally AgPb2.40Mn1.60Sb3As2S12, is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as black, anhedral to subhedral grains up to 200 µm across, closely associated with orpiment, tennantite/tetrahedrite, other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S, and calcite. Menchettiite is opaque with a metallic luster and possesses a black streak. It is brittle, with uneven fracture; the Vickers microhardness (VHN100) is 128 kg/mm2 (range 119–136) (corresponding to a Mohs hardness of 2½–3). The calculated density is 5.146 g/cm3 (on the basis of the empirical formula). In plane-polarized incident light, menchettiite is weakly to moderately bireflectant and weakly pleochroic from dark gray to a dark green. Internal reflections are absent. Between crossed polarizers, the mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) for the four standard COM wavelengths are 33.1, 39.8 (471.1 nm), 31.8, 38.0 (548.3 nm), 30.9, 37.3 (586.6 nm), and 29.0, 35.8 (652.3 nm), respectively.Menchettiite is monoclinic, space group P21/n, with unit-cell parameters: a = 19.233(2), b = 12.633(3), c = 8.476(2) Å, ß = 90.08(2)°, V = 2059.4(8) Å3, a: b: c 1.522:1:0.671, Z = 2, and it is twinned on {100}. The crystal structure was refined to R = 0.0903 for 2365 reflections with Fo 〉 4s(Fo) and it resulted to be topologically identical to those of ramdohrite, uchucchacuaite, and fizélyite. The six strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 3.4066 (39) (3¯12), 3.4025 (39) (312), 3.2853 (100) (520), 2.8535 (50) (2¯32), 2.8519 (47) (232), and 2.1190 (33) (004). Electron-microprobe analyses gave the chemical formula Ag1.95Cu0.01Pb4.81Mn3.20Fe0.02Zn0.01Sb6.09As3.94Bi0.01S23.95Se0.01, on the basis of 44 atoms and according to the structure refinement results. Menchettiite can be classified among the Sb-rich members of the lillianite homeotypic series, which are described with the general formula AgxPb3-2xSb2+xS6. Besides the heterovalent substitution 2Pb2+ ? Ag+ + Sb3+ taken into consideration by the above formula, two isovalent substitutions relate menchettiite to the other lillianite homeotypes, i.e., Mn2+ ? Pb2+ and As3+ ? Sb3+. The name is after Silvio Menchetti (1937–), Professor of Mineralogy and Crystallography at the University of Florence. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2011–009).

Description: Secondary organic aerosol (SOA) in the southeastern US is investigated by analyzing the spatial-temporal distribution of water-soluble organic carbon (WSOC) and other PM2.5 components from 900 archived 24-h Teflon filters collected at 15 urban or rural EPA Federal Reference Method (FRM) network sites throughout 2007. Online measurements of WSOC at an urban/rural-paired site in Georgia in the summer of 2008 are contrasted to the filter data. Based on FRM filters, excluding biomass-burning events (levoglucosan 〈 50 ng m−3), WSOC and sulfate were highly correlated with PM2.5 mass (r2~0.7). Both components comprised a large mass fraction of PM2.5 (13% and 31%, respectively, or ~25% and 50% for WSOM and ammonium sulfate). Sulfate and WSOC both tracked ambient temperature throughout the year, suggesting the temperature effects were mainly linked to faster photochemistry and/or synoptic meteorology and less due to enhanced biogenic hydrocarbon emissions. FRM WSOC, and to a lesser extent sulfate, were spatially homogeneous throughout the region, yet WSOC was moderately enhanced (27%) in locations of greater predicted isoprene emissions in summer. A Positive Matrix Factorization (PMF) analysis identified two major source types for the summer WSOC; 22% of the WSOC were associated with ammonium sulfate, and 56% of the WSOC were associated with brown carbon and oxalate. A small urban excess of FRM WSOC (10%) was observed in the summer of 2007, however, comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008 showed substantially greater difference in WSOC (31%) relative to the FRM data, suggesting a low bias for urban filters. The measured Atlanta urban excess, combined with the estimated boundary layer heights, gave an estimated Atlanta daily WSOC production rate in August of 0.55 mgC m−2 h−1 between mid-morning and mid-afternoon. This study characterizes the regional nature of fine particles in the southeastern US, confirming the importance of SOA and the roles of both biogenic and anthropogenic emissions.

Description: Secondary organic aerosol (SOA) in the Southeastern US is investigated by analyzing the spatial-temporal distribution of water-soluble organic carbon (WSOC) and other PM2.5 components from 900 archived 24 h Teflon filters collected at 15 urban or rural EPA Federal Reference Method (FRM) network sites throughout 2007. Online measurements of WSOC at an urban/rural-paired site in Georgia in the summer of 2008 are contrasted to the filter data. Based on FRM filters, excluding biomass-burning events (levoglucosan 〈 50 ng m−3), WSOC and sulfate were highly correlated with PM2.5 mass and both comprised a large mass fraction of PM2.5 (13% and 35%, respectively). Sulfate and WSOC both tracked ambient temperature throughout the year, suggesting the temperature effects were mainly on the photochemical processes that lead to secondary formation. FRM WSOC, and to a lesser extent sulfate, were spatially homogeneous throughout the region, yet WSOC was moderately enhanced (27%) in locations of greater predicted isoprene emissions in summer. A Positive Matrix Factorization (PMF) analysis identified two major source types for the summer WSOC; 22% of the WSOC were associated with ammonium sulfate, and 56% of the WSOC was associated with brown carbon and oxalate. A small urban excess of FRM WSOC (10%) was observed in the summer of 2007, however, comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008 showed substantially greater difference in WSOC (31%) relative to the FRM data, suggesting a low bias for urban filters. The measured Atlanta urban excess, combined with the estimated boundary layer heights, gave an estimated Atlanta daily WSOC production rate in August of 0.55 mg C m−2 h−1 between mid-morning and mid-afternoon. This study characterizes the regional nature of fine particles in the Southeastern US, confirming the importance of secondary organic aerosol and the roles of both biogenic and anthropogenic emissions.

Description: Here we show the use of the 210Pb-226Ra excess method to determine the growth rate of two corals from the world's largest known cold-water coral reef, Røst Reef, north of the Arctic circle off Norway. Colonies of each of the two species that build the reef, Lophelia pertusa and Madrepora oculata, were collected alive at 350 m depth using a submersible. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and trace element compositions were studied. 210Pb and 226Ra differ in the way they are incorporated into coral skeletons. Hence, to assess growth rates, we considered the exponential decrease of initially incorporated 210Pb, as well as the increase in 210Pb from the decay of 226Ra and contamination with 210Pb associated with Mn-Fe coatings that we were unable to remove completely from the oldest parts of the skeletons. 226Ra activity was similar in both coral species, so, assuming constant uptake of 210Pb through time, we used the 210Pb-226Ra chronology to calculate growth rates. The 45.5 cm long branch of M. oculata was 31 yr with an average linear growth rate of 14.4 ± 1.1 mm yr−1 (2.6 polyps per year). Despite cleaning, a correction for Mn-Fe oxide contamination was required for the oldest part of the colony; this correction corroborated our radiocarbon date of 40 yr and a mean growth rate of 2 polyps yr−1. This rate is similar to the one obtained in aquarium experiments under optimal growth conditions. For the 80 cm-long L. pertusa colony, metal-oxide contamination remained in both the middle and basal part of the coral skeleton despite cleaning, inhibiting similar age and growth rate estimates. The youngest part of the colony was free of metal oxides and this 15 cm section had an estimated a growth rate of 8 mm yr−1, with high uncertainty (~1 polyp every two to three years). We are less certain of this 210Pb growth rate estimate which is within the lowermost ranges of previous growth rate estimates. We show that 210Pb-226Ra dating can be successfully applied to determine the age and growth rate of framework-forming cold-water corals if Mn-Fe oxide deposits can be removed. Where metal oxides can be removed, large M. oculata and L. pertusa skeletons provide archives for studies of intermediate water masses with an up to annual time resolution and spanning over many decades.