To calibrate infrared (IR) spectroscopy for quantitative analysis of trace structural OH in specific minerals, we have determined concentrations of H in pure separates of mantle derived pyrope garnet (56 ± 6 ppm H_2O by weight), augite (268 ± 8, ppm H_2O, and enstatite (217 ± 11 ppm H_2O) by manometry after heating the samples and extracting H_2 gas under vacuum. IR spectroscopy confirmed the presence of intrinsic OH in these samples prior to extraction and indicated between 86 and 100% removal of H during the extraction procedure. The integral specific absorption coefficients of 1.39 ± 0.14(lσ),7.09
± 0.32, and 15.6 ± 0.94 /(ppm H_2O.cm^2) for pyrope, augite, and enstatite, respectively, allow precise spectroscopic determination of the OH content of upper mantle garnets and pyroxenes to concentration levels of a few parts per million. Uncertainties in accuracy depend on mineral composition and characteristics of the OH absorption spectrum and are estimated to range between ± 10 and ± 50%.

http://minsocam.org/msa/ammin/toc/articles_free/1995/bell_p465-474_95.pdf

Quantitative analysis of trace OH in garnet and pyroxenes

Pyroxene reflectance and transmittance spectra have been examined in a search for systematic relationships between spectral features and compositional variations and to assess the applicability of reflectance spectroscopy to pyroxene geothermometry. Orthopyroxenes containing up to about 11 percent Wollastonite show a positive correlation between Fe(2+) content and wavelength positions of the major absorption bands. Aluminum-rich orthopyroxenes display absorption bands at lower than expected wavelengths. Spectral-compositional relationships are more complex for clinopyroxenes, showing both positive and negative correlations between band positions and major cation abundances. These relationships are further complicated by the presence of significant amounts of other transition series elements such as Ti and Cr and by the presence of exsolved phases and compositional zonations. Contours of the wavelength positions of band minima projected onto the pyroxene tetralateral generally exhibit concave downward shapes. The orientations of the contours relative to pyroxene geotherms are such as to effectively preclude the use of spectroscopy to significantly constrain the temperatures of formation of pyroxenes.

/pdf/pyroxene-spectroscopy-revisited-spectral-compositional-2x693vwhuh.pdf

Pyroxene spectroscopy revisited - Spectral-compositional correlations and relationship to geothermometry

Geochemical and Sr–Nd–Pb–O isotopic compositions of the post-collisional ultrapotassic magmatism in SW Tibet: Petrogenesis and implications for India intra-continental subduction beneath southern Tibet

— Calcium- and aluminum-rich inclusions (CAIs), chondrules, dark inclusions and matrices in certain CV3 carbonaceous chondrites appear to have been modified by different degrees of late-stage alteration processes that caused significant variations in mineralogy and chemistry. Some chondrules and CAIs are rimmed with fayalitic olivine. Metal in all components may be oxidized and sulphidized to magnetite, Ni-rich metal and sulfides. Silicates in all components are aqueously altered to different degrees to phyllosilicates. Primary minerals in some CAIs experienced Fe-alkali-halogen metasomatism forming nepheline, sodalite, wollastonite, hedenbergite and other secondary minerals. In CV3 chondrites with metasomatized CAIs, nepheline, sodalite, etc. are also present in chondrule mesostases and in matrices. McSween's (1977b) reduced subgroup of CV3 chondrites generally shows minimal alteration of all components and may represent the unaltered precursors for the oxidized CV3 chondrites, which generally show major alteration. Most studies have been focused on specific components in CV3 chondrites and have not considered possible relationships between alteration processes. We infer from the correlated occurrences of the alteration features that they were closely related in time and space and review nebular and asteroidal models for their origins. We prefer an asteroidal model.

Mineralogical and chemical modification of components in CV3 chondrites: Nebular or asteroidal processing?

### Dashkovaite*

N.V. Chukanov, D.I. Belakovsky, S.V. Malinko, N.I. Organova (2000) Dashkovaite Mg(HCO3)2·2H2O — A new formate mineral. Zapiski Vseross. Mineral. Obshch., 129(6), 49–53 (in Russian, English abs.).

Chemical analysis gave C 16.2, H 3.9, Mg 16.4, Mn (by electron microprobe) 0.2, O (by difference) 63.3, sum 100 wt%, corresponding to Mg1.00Mn0.01H5.74C2.00O5.87, ideally Mg(HCO3)2 2H2O. The mineral occurs as white, fibrous aggregates in hydrothermal veinlets, up to 1 mm in width, wherein the fibers are up to 3 mm long and 0.01 mm wide. Soft and porous, H = 1, D calc = 1.74 g/cm3 for Z = 4. Microscopically colorless, biaxial positive, α = 1.465(3), α = 1.486(3), γ = 1.516(3), 2 V calc = 81(5)°, X parallel to the elongation. By analogy with the synthetic analog, indexing of the X-ray powder pattern gave a monoclinic cell, space group P 21/ c , a = 8.64(1), b = 7.15(1), c = 9.38(1) A, α = 98.0(1) °; strongest lines of the pattern (57 mm camera, Fe K α radiation) are 4.90(90,111), 4.64(80,002), 4.30(70,200), 3.68(80,210), and 3.40(100,112). The IR spectrum is similar to that of the synthetic compound.

The mineral occurs with shabynite, iowaite, ekaterinite, korshunovskite, halite, hydromagnesite, and serpentine in dolomite marble at the Korshunovskoye boron deposit in the Irkutsk district, Siberia. The new mineral name is for E.R. Dashkova (1744–1810), former Director of the Saint Petersburg Academy of Sciences (1783–1796) and President of the Russian Academy of Sciences. Type material is in the Fersman Mineralogical Museum, Moscow, Russia. J.L.J. 

### Fluorannite*

Ganfu Shen, Qi Lu, Jinsha Xu (2000) Fluorannite: A new mineral of the mica group from the western suburb of Suzhou City. Acta Petrologica Mineral., 19(4), 355–362 …

New mineral names

La Sous-Commission Pyroxenes creee par la Commission Nouveaux Mineraux et Noms de Mineraux (C.N.M.M.N.) de l'Association Mineralogique Internationale (I.M.A.) presente son rapport final sur la nomenclature des pyroxenes. Les recommandations de la Sous-Commission proposees dans ce rapport ont ete officiellement acceptees par la Commission. Des noms acceptes et largement utilises ont ete definis chimiquement, combinant des methodes nouvelles et conventionnelles, de facon a etre en accord dans la mesure du possible avec l'usage actuel generalement admis. Vingt noms ont ete officiellement acceptes, parmi eux treize sont employes pour representer des poles purs de composition chimique bien determinee. Dans les solutions solides binaires ordinaires, les noms d'especes sont donnes par les termes extremes suivant la \"regle des 50%\". Des adjectifs modificatifs sont ajoutes aux noms des pyroxenes pour indiquer des quantites exceptionnelles de constituants chimiques. Ce rapport inclut une liste de 105 noms de pyroxene utilises precedemment, qui ont ete rejetes officiellement par la Commission.

K. Aoki

Papers

Nomenclature of pyroxenes.

Nomenclatura de piroxenos