Ferrochiavennite: um novo zeólito

FERROCHIAVENNITE, A NEW BERYLLIUM SILICATE ZEOLITE FROM SYENITE PEGMATITES IN THE LARVIK PLUTONIC COMPLEX, OSLO REGION, SOUTHERN NORWAY

Resumo:
Ferrochiavennite is a new beryllium silicate zeolite with chemical composition close to Ca1–2FeSi5Be2O13(OH)2·2H2O. It is described from two syenite pegmatite localities in Norway: Blåfjell, Langangen, Telemark, and the AS Granit larvikite quarry, Tvedalen, Vestfold. The mineral is monoclinic, P21/c, with a 8.759(5), b 4.864(2), c 31.258(6) Å, β 90.31(6)°, V 1331.7(6) Å3, and Z = 4. The crystal structure was refined to R1 = 0.048 for 3651 observed reflections. The zeolite structure is isostructural with chiavennite, consisting of intersecting channels of nine-, six-, five-, and four-fold rings. The strongest eight reflections of the X-ray powder-diffraction pattern [d(obs.) in Å (I) (hkl)] are: 15.555 (100) (002), 4.104 (29) (1̅12, 112), 3.938 (36) (1̅13, 113), 3.909 (60) (008), 3.820 (30) (2̅04, 204), 3.251 (66) (017, 210, 2̅11), 3.186 (27) (2̅12, 212), 2.884 (64) (2̅15, 215). The mineral is biaxial (+) with refractive indices α 1.583(1), β 1.589(1), γ 1.602(1), measured at 590 nm. 2V (meas.) = 62(4)° from extinction curves 2V = 76(5)°; 2V (calc.) = 69°. The optical orientation is X ~ a, Y ~ c, and Z ~ b. The Mohs hardness is ~ 3; D(meas.) = 2.67(2) and D(calc.) = 2.709 g/cm3.

Grice, J. D., Kristiansen, R., Friis, H., Rowe, R., Poirier, G.G., Selbekk, R.S., Cooper, M.A. & Larsen, A.O. (2013): Ferrochiavennite, a new beryllium silicate zeolite from syenite pegmatites in the Larvik Plutonic Complex, Oslo region, Southern Norway. Canadian Mineralogist. 51: 285-296

Anúncios

~ por Ricardo Pimentel em Junho 23, 2013.

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