IMA 2017-051 = beusite-(Ca)

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Marco E. Ciriotti
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IMA 2017-051 = beusite-(Ca)

Messaggio da Marco E. Ciriotti » mer 30 mag, 2018 13:50

Prossima pubblicazione.

Referenza:
▪ Hawthorne, F.C., Wise, M.A., Černý, P., Abdu, Y.A., Ball, N.A., Pieczka, A., Włodek, A. (2018): Beusite-(Ca), ideally CaMn2+2(PO4)2, a new graftonite-group mineral from the Yellowknife pegmatite field, Northwest Territories, Canada: Description and crystal structure. Mineralogical Magazine, 82, (in press).
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 25117
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: IMA 2017-051 = beusite-(Ca)

Messaggio da Marco E. Ciriotti » lun 28 gen, 2019 15:21

Referenza:
▪ Hawthorne, F.C., Wise, M.A., Černý, P., Abdu, Y.A., Ball, N.A., Pieczka, A., Włodek, A. (2018): Beusite-(Ca), ideally CaMn2+2(PO4)2, a new graftonite-group mineral from the Yellowknife pegmatite field, Northwest Territories, Canada: Description and crystal structure. Mineralogical Magazine, 82, 1323-1332.

Abstract:
Beusite-(Ca), ideally CaMn2+(PO4)2, is a new graftonite-group mineral from the Yellowknife pegmatite field, Northwest Territories, Canada. It occurs in a beryl–columbite–phosphate rare-element pegmatite where it is commonly intergrown with triphylite–lithiophilite or sarcopside, and may form by exsolution from a high-temperature (Li,Ca)-rich graftonite-like parent phase. It occurs as pale-brown lamellae 0.1–1.5 mm wide in triphylite, and is pale brown with a vitreous lustre and a very pale-brown streak. It is brittle, has a Mohs hardness of 5, and the calculated density is 3.610 g/cm3. Beusite-(Ca) is colourless in plane-polarized light, and is biaxial (+) with α = 1.685(2), β = 1.688(2), γ = 1.700(5), and the optic axial angle is 46.0(5)°. It is non-pleochroic with X || b; Y ˄ a = 40.3° in β obtuse; Z ˄ a = 49.7° in β acute. Beusite-(Ca) is monoclinic, has space group P21/c, a = 8.799(2), b = 11.724(2), c = 6.170(1) Å, β = 99.23(3)°, V = 628.3(1) Å3 and Z = 4. Chemical analysis by electron microprobe gave P2O5 41.63, FeO 19.43, MnO 23.63, CaO 15.45, sum 100.14 wt.%. The empirical formula was normalized on the basis of 8 anions pfu: (Ca0.94Fe0.92Mn1.13)Σ2.99(PO4)2.00. The crystal structure was refined to an R1 index of 1.55%. Beusite-(Ca) is a member of the graftonite group with Ca completely ordered at the [8]-coordinated M(1) site.
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