27 research outputs found

    A1: Lithium-Boron-Beryllium Gem Pegmatites, Oxford Co., Maine: Havey and Mount Mica Pegmatites

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    Guidebook for field trips in Western Maine and Northern New Hampshire: New England Intercollegiate Geological Conference, p. 1-34

    Size Distributions of Coastal Ocean Suspended Particulate Inorganic Matter: Amorphous Silica and Clay Minerals and their Dynamics

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    Particulate inorganic matter (PIM) is a key component in estuarine and coastal systems and plays a critical role in trace metal cycling. Better understanding of coastal dynamics and biogeochemistry re-quires improved quantification of PIM in terms of its concentration, size distribution, and mineral species composition. The angular pattern of light scattering contains detailed information about the size and composition of particles. These volume scattering functions (VSFs) were measured in Mobile Bay, Alabama, USA, a dynamic, PIM dominated coastal environment. From measured VSFs, we determined through inversion the particle size distributions (PSDs) of major components of PIM, amorphous silica and clay minerals. An innovation here is the extension of our reported PSDs significantly into the sub-micron range. The PSDs of autochthonous amorphous silica exhibit two unique features: a peak centered at about 0.8mm between 0.2 and 4mm and a very broad shoulder essentially extending from 4mm to\u3e100mm. With an active and steady particle source from blooming diatoms, the shapes of amorphoussilica PSDs for sizes area, but showed more particles of sizes\u3e10mm inside the bay, likely due to wind-induced resuspension of larger frustules that have settled. Compared to autochthonous amorphous silica, the allochthonous clay minerals are denser and exhibit relatively narrower PSDs with peaks located between 1 and 4mm. Preferential settling of larger mineral particles as well as the smaller but denser illite component further narrowed the size distributions of clay minerals as they were being transported outside the bay. The derived PSDs also indicated a very dynamic situation in Mobile Bay when a cold weather front passed through during the experiment. With northerly winds of speeds up to 15 m s-1, both amorphous silica and clay minerals showed a dramatic increase in concentration and broadening in size distribution outside the exit of the barrier islands, indicative of wind-induced resuspension and subsequent advection of particles out of Mobile Bay. While collectively recognized as the PIM, amorphous silica and clay minerals, as shown in this study, possess very different size distributions. Considering how differences in PSDs and the associated particle areas will effect differences in sorption/desorption properties of these components, the results also demonstrate thepotential of applying VSF-inversion in studying biogeochemistry in the estuarine-coastal ocean system

    The challenge of the identification of a new mineral species: example "Pezzottaite"

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    In 2002, a new gem mineral of commercial importance was discovered. In accordance with the need for all new mineral discoveries to be scientifically characterized (see Nickel and Grice, 1998), the gemological community anxiously awaited the results of tests to positively identify the new mineral (Hawthorne et al., 2003, Hawthorne et al., submitted and Laurs et al., 2003). This period of analysis brought into play the question: Exactly what procedures are necessary for the positive characterization of a new mineral

    The Contrasting Effects between Caffeine and Theobromine on Crystallization: How the Non-fluoride Dentifrice Was Developed

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    Caffeine and theobromine are members of the xanthine family. Coffee and soft drinks contain caffeine, whereas, in cacao, theobromine is the main ingredient. The mineral contents of the tooth which sucked the caffeine-containing dam’s milk were decreased. To determine if caffeine would affect enamel, dams were fed with a caffeine and pups were killed and first and second molars were extracted. Enamel was exposed to the acid solution and dissolved minerals from the enamel were measured. Calcium, phosphorus and magnesium from the first molars of the caffeine group were significantly dissolved. To determine why minerals were released, enamel was separated. The crystallite size of the enamel from the caffeine group showed decreased. If the pups with the same dietary regimen, but given a cariogenic diet, the caffeine group should show a higher incidence of dental caries. The caffeine group revealed higher caries scores. An in vitro experiment to grow apatite crystals was conducted, adding the various members of the xanthine. Theobromine produced larger crystal sizes than caffeine. Theobromine was added to the maternal diet. Dissolution experiments revealed that these minerals were far less dissolved. Comparative studies of the various parameters between theobromine and fluoride were conducted. Theobromine was superior to fluoride in every aspect

    Galliskiite, Ca4Al2 (PO4) 2F8·5H2O, a new mineral from the Gigante granitic pegmatite, Có;rdoba province, Argentina

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    Galliskiite, ideally Ca4Al2 (PO4) 2F8·5H2O, is a new mineral found at the Gigante granitic pegmatite, Punilla department, CĂł;rdoba Province, Argentina. It is named for Argentine mineralogist and pegmatite specialist Miguel Á;ngel Galliski. Galliskiite is triclinic, P1̄, a = 6.1933(7), b = 9.871(1), c = 13.580(2) Å, α = 89.716(3), ÎČ = 75.303(4), Îł = 88.683(4)°, Z = 2. The strongest lines in the X-ray powder dif-fraction pattern are [d in Å, (I)]: 7.904 (70), 5.994 (100), 3.280 (58), 3.113 (30), 2.945 (85), 2.887 (44), 2.483 (20), 2.262 (27), 2.150 (23), 1.821 (27), and 1.798 (25). It occurs as crude platy crystals elongated along [001] and flattened on {010}, with frosty surfaces. Simple contact and polysynthetic twinning on {100} by rotation about [010] is ubiquitous. It is colorless and transparent, has white streak and vitreous luster, and is nonfluorescent under ultraviolet radiation. It has a Mohs hardness of 21/2, conchoidal to irregular fracture and two fair cleavages at approximately 90°. The measured density is 2.67(3) g/cm3, and the calculated density is 2.670 g/cm3. Galliskiite dissolves slowly in concentrated HCl. The mineral is biaxial (+), α = 1.493(1), ÎČ = 1.495(1), Îł = 1.520(1), 2Vmeas = 33(5)°, 2Vcalc = 32°; dispersion, r < v; orientation Z ≈ b, X and Z at 40-50° from a and c. No pleochroism is observed. Analysis by electron microprobe (average of 12 analyses given in wt%) provided CaO 34.71, MgO 0.01, FeO 0.10, MnO 0.17, Al 2O3 15.92, SiO2 0.06, TiO2 0.01, P2O5 21.94, F 21.35, H2O (calculated by stoichiometry) 15.08, less F=O 8.99, total 100.39 wt%. The empirical formula, based on 21 (F+O), is (Ca3.98Mn0.02Fe0.01) Al2.01 (P1.99Si0.01O8)F 7.23 (OH)0.77 ·5H2O. The crystal structure, solved and refined using single-crystal data to R1 = 0.033, consists of double chains of alternating corner-sharing AlF 3O3 octahedra and PO4 tetrahedra along the a axis. The chains are joined into a framework via bonds to four distinct Ca atoms. Calcium atoms are also linked by sharing isolated F atoms and H 2O molecules. The double-chain motif in the structure of galliskiite is distinct from that in any other known phosphate.Fil: Kampf, Anthony R.. Natural History Museum Of Los Angeles County; Estados UnidosFil: Colombo, Fernando. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - CĂłrdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Simmons, William B.. University of New Orleans; Estados UnidosFil: Falster, Alexander U.. University of New Orleans; Estados UnidosFil: Nizamoff, James W.. University of New Orleans; Estados Unido

    Yellow muscovite from Brazil

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    Micas are rarely faceted due to their softness (Mohs 2Âœ) and perfect cleavage, but occasionally compact aggregates showing an attractive color are polished into beads, carvings, objets d’art, or even faceted stone. At the 2010 Tucson gem shows, a new gem-quality yellow mica debuted from Itinga in the AraçuaĂ­ pegmatite district, Minas Gerais, Brazil (e.g., figure 23). It was sold as yellow lepidolite by most dealers or as muscovite (M. MacrĂŹ, “Lepidolite gialla di qualitĂ  gemma,” Rivista Gemmologica Italiana, Vol. 5, No. 3, 2010, pp. 234– 235). A faceted stone and cabochon were donated to the GIA Collection by Mauro PantĂČ (The Beauty in the Rocks, Laigueglia, Italy). Mr. PantĂČ has polished approximately 1,000 carats of faceted stones and 2,000 carats of cabochons, ranging from 4 to 12 ct