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Mineralogical ClassificationIMA2013-063 = Oxynatromicrolite

15th Jul 2017 15:18 UTCLuc Vandenberghe Expert

Reference : FAN GUANG, GE XIANGKUN, LI GUOWU, YU APENG, SHEN GANFU : Oxynatromicrolite, (Na,Ca,U)2Ta2O6(O,F), a new member of the pyrochlore supergroup from Guanpo, Henan Province, China, Mineralogical Magazine, 2017, Vol. 0(0), pp. 1–9

Abstract :

A new mineral species of the pyrochlore supergroup, oxynatromicrolite (IMA2013-063), (Na,Ca,U)2Ta2O6O, was found in the No. 309 rare-metal granitic pegmatite vein, Guanpo, Lushi county,Henan province, China, which is characterized by tantalum at the B site and oxygen at the Y site and is Nadominant at the A site.

The mineral occurs as strongly metamict, and mostly euhedral octahedral crystals up to 0.05–0.20 mmacross. The measured density of an unheated sample is 6.580(4) g cm–3, and the calculated one is 6.506 g cm–3. Optically, the mineral is isotropic, with an index of refraction 1.999(5) and a reflectance of 11.88% (470 nm).

When heated to 1000°C for 4 hours in N2, the mineral recrystallizes in the cubic system, with space group Fd3m and with unit-cell parameters similar those of other pyrochlore supergroup species: a = 10.420(6) Å, V = 1131.4(2) Å3. Electron microprobe analyses revealed the following composition of the mineral (in wt.%): Na2O 5.41, CaO 4.56, UO2 14.60, La2O3 0.16, Ce2O3 0.11, Nd2O3 0.13, PbO 0.62, Ta2O5 61.52, Nb2O5 8.21, Sb2O5 0.23, TiO2 0.05, SiO2 0.56, SnO2 0.29, F 1.04, H2O 1.50 (calculated to correspond to 0.47 H2O pfu), F≡O –0.44, sum = 98.53%, which corresponds to the

empirical formula (Na0.99Ca0.46U0.31Pb0.02 La0.01H2O0.21)Σ2.00 (Ta1.58Nb0.35Si0.05Sn0.01Sb0.01)Σ2.00O6 (O0.43F0.31H2O0.26)Σ1.00, represented by the simplified formula (Na,Ca,U)2(Ta,Nb)2O6(O,F).

Oxynatromicrolite crystallized during the late-stage of formation for the No. 309 pegmatite dyke and is associated with quartz, albite, potassium feldspar, muscovite, kaolinite, tantalite-Mn, stibiotantalite, pollucite, spodumene, montebrasite, Hf-rich zircon, a red tourmaline, polylithionite, trilithionite, luanshiweiite-2M1(IMA2011-102) and a hydrated derivative of oxynatromicrolite.

15th Jul 2017 19:42 UTCPavel Kartashov Manager

Old kind djalmaite. :-)

And of course I don't believe, that this is oxy- specie. Because of metamict oxy-species in pyrochlore supergroup are obvious nonsence.

Really its formula is (Na_0.99Ca_0.46U_0.31Pb_0.02La_0.01)_Σ1.79 (Ta_1.58Nb_0.35Si_0.05Sn_0.01Sb_0.01)_Σ2.00O₆(OH_0.53F_0.31)_Σ0.84, so it is hydroxynatromicrolite.

Obviously CNM stopped catching mice... :-(

16th Jul 2017 09:24 UTCMarco E. Ciriotti Manager

Publication is done:

Reference:

▪ Fan, G., Ge, X., Li, G., Yu, A., Shen, G. (2017): Oxynatromicrolite, (Na,Ca,U)₂Ta₂O₆(O,F), a new member of the pyrochlore supergroup from Guanpo, Henan Province, China. Mineralogical Magazine, 81, 743-751.

17th Jul 2017 15:17 UTCLuc Vandenberghe Expert

Mario,

I just have the paper for proof...

Would you be so kind, if you have, send me the definitive version of this work ???

Thank you in advance.

Luc

19th Jul 2017 06:41 UTCMarco E. Ciriotti Manager

Done, Luc.

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