The crystal chemistry of roméite

Brugger, Joël; Gieré, Reto; Graeser, Stefan; Meisser, Nicolas

doi:10.1007/s004100050271

Cited by 43 publications

(39 citation statements)

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“…The structure of ideal pyrochlore group, is a derivative of the fluorite structure (chakouMakos, 1984(chakouMakos, , 1986. The structure with Ta, Nd, and Ti, and which can also contain Fe, Sn, W, and Sb (ManDarino, 1999); Sb 5+ can even dominate at the B site, as in the case of roméite (BruGGer et al, 1997). The A site is eight coordinated (distorted cube) and may contain alkalis, alkaline earths, REE and actinides.…”

Section: Thorium Mineralizationsmentioning

confidence: 99%

Mineral chemistry and genesis of Zr, Th, U, Nb, Pb, P, Ce and F enriched peralkaline granites of El-Sibai shear zone, Central Eastern Desert, Egypt

Ali¹

2013

Geologija

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Section: Thorium Mineralizationsmentioning

confidence: 99%

Mineral chemistry and genesis of Zr, Th, U, Nb, Pb, P, Ce and F enriched peralkaline granites of El-Sibai shear zone, Central Eastern Desert, Egypt

Ali¹

2013

Geologija

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“…The low totals of the chemical analyses are due to the porous nature of the samples and the presence of molecular water. Likewise, Brugger et al (1997) reported a significant content of H 2 O, up to 14 wt. % in roméite from Massiac (France).…”

Section: Chemical Compositionmentioning

confidence: 95%

“…This value is somewhat lower than the theoreti cal content of 37.3 wt. % H 2 O, which is probably due to (Brugger et al 1997). Asite is occu pied by Ca, Na, Ba, Bi, Sb, REE and other elements; the value m denotes vacancy or H 2 O content, which are both common in these minerals (Brugger et al 1997 The chemical composition of white roméite is charac terized by dominant vacancy or H 2 O content (1.22-1.28 pfu) and high contents of Ca (0.72-0.77 apfu) in the Asite.…”

Section: Chemical Compositionmentioning

confidence: 99%

The supergene mineral association with brandholzite from Pernek, Malé Karpaty Mountains, Slovak Republic

Sejkora¹,

Ozdín²,

Ďuďa³

2012

J. Geosci.

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Brandholzite, a hydrated hydroxide of Mg 2+ and Sb 5+, was found at the Krížnica deposit near Pernek (Malé Karpaty Mountains, Slovak Republic); it is the third occurrence of this mineral phase worldwide. Crystals and crusts of brand holzite occur as surface coatings on altered shales mineralized with stibnite and pyrite. Associated minerals include roméitelike phases, sulphur, aragonite, gypsum, sénarmontite and Sbrich Fehydroxides. Brandholzite forms euhedral tabular crystals of hexagonal habit, typically 0.5 to 0.8 mm across, exceptionally up to 2 mm long. 6 ] 2.00 . The XRD pattern was indexed in a trigonal setting (space group P3), with refined unitcell parameters a = 16.1076(9), c = 9.8628(9) Å and V = 2216.1(2) Å 3 . The thermogravimetric curve shows total weight loss of 34.6 wt. % (over the interval of 20-800 °C), caused by H 2 O release. The initial rapid weight decrease (20-140 °C) was followed by a minor continuous weight loss up to 800 °C. Brandholzite from Pernek and its mineral association were probably formed by subrecent weathering processes in an abandoned mines environment.

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“…Minerals of the pyrochlore group conform to the simplified general formula where A = Ca, Na, actinides, rare earth elements (REE), Ba, Sr, Bi, Pb; 1?= Nb, Ta, Ti, Zr, Sb, W, Fe; X = O, OH, and Y = O, OH, F. On the basis of the B-site cations, three subgroups are commonly distinguished within the pyrochlore group [3]: (1) pyrochlore sensu stricto (Nb-rich), (2) rnicrolite (Ta-rich), and (3) betafite (Ti-rich). A fourth subgroup, rom6ite (Sb-rich), was recently suggested by Brugger et al [4]. Synthetic pyrochlore-group phases are also prominent actinide hosts in polyphase crystalline and certain glass-ceramic waste forms designed for the immobilization of high level nuclear waste [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…Pyrochlore and betafite are typical accessory minerals in carbonatites, and occur in various pegmatites, syenites and related alkaline rocks, and in some hydrothermal veins. Microlite is found primarily in granitic pegmatites, whereas rom6ite typically occurs in metamorphosed Mn deposits and hydrothermal veins [4,7,8]. The pyrochlore-group minerals provide excellent natural analogues for pyrochlore-based nuclear waste forms, because samples of variable age and with high actinide contents are available.…”

Section: Introductionmentioning

confidence: 99%