Trinepheline and fabriesite: two new mineral species from the jadeite deposit of Tawmaw (Myanmar)

Research areas:

• Surfaces planétaires (2011 - 2016)

Year:

2014

Authors:

• Cristiano Ferraris
• Gian Carlo Parodi
• Sylvain Pont
• Benjamin Rondeau
• Jean-Pierre Lorand

Journal:

EUROPEAN JOURNAL OF MINERALOGY

Volume:

26

Number:

2

Pages:

257-265

Month:

March

ISSN:

0935-1221

BibTex:

@article{WOS:000334918100006, author = "Cristiano Ferraris and Gian Carlo Parodi and Sylvain Pont and Benjamin Rondeau and Jean-Pierre Lorand", abstract = "Two new mineral species, trinepheline (NaAlSiO4) and fabriesite (Na3Al3Si3O12 center dot 2H(2)O), are described from late-stage metamorphic veins of the jadeite deposit of Tawmaw-Hpakant (Myanmar). Both minerals and their names were approved by the IMA Commission on New Minerals and Mineral Names (IMA 2012-024 and IMA 2012-080). The name trinepheline is known in literature for the polymorphs of synthetic NaAlSiO4 with a value of the c parameter that is three times that of nepheline. Fabriesite is named in memory of Jacques Fabrie{\&}#039;s (1932-2000), former professor of the ``Museum National d{\&}#039;Histoire Naturelle{{\&}#039;{\&}#039;} in Paris (France). Fabriesite and trinepheline occur intimately intergrown together with nepheline, more rarely with albite and other feldspar-group phases such as banalsite and stronalsite; other associated minerals are jadeite and secondary products like natrolite and harmotome. All phases have been identified via electron backscatter diffraction (EBSD) patterns. Both fabriesite and trinepheline are pseudomorph after jadeite and occur as skeletal allotriomorphic crystals up to 15-20 mu m long and 5-10 mu m wide. They are white to yellowish in hand specimen, colourless in thin section; the streak is white and the lustre appears vitreous to greasy; they are non-fluorescent; Mohs{\&}#039; hardness is 5-51/2. Empirical formulae (EMPA analysis) are very close to the ideal compositions with traces of Ca and K for trinepheline, and of Ca, K, Ba, Mg, Fe, and Mn for fabriesite. Calculated densities are 2.642 g cm(-3) for trinepheline (space group P6(1), a = 9.995 angstrom, c = 24.797 angstrom) and 2.386 g cm(-3) for fabriesite (space group Pna2(1), a = 16.426 angstrom, b = 15.014 angstrom, c = 5.223 angstrom), respectively. The strongest five lines in the calculated X-ray powder diffraction patterns {[}d (angstrom) (I)(hkl)] are: 3.163(100)(122), 3.834(81)(023), 4.133(49)(006), 3.272(40)(120) and 2.403(31)(127) for trinepheline; 3.41(100)(240), 4.41(77)(201), 2.97(70)(421), 2.61(40)(002) and 8.21(36)(200) for fabriesite.", doi = "10.1127/0935-1221/2014/0026-2348", extra = "PICL", issn = "0935-1221", journal = "EUROPEAN JOURNAL OF MINERALOGY", month = "MAR", number = "2", pages = "257-265", title = "{T}rinepheline and fabriesite: two new mineral species from the jadeite deposit of {T}awmaw ({M}yanmar)", volume = "26", year = "2014", }

Abstract:

Two new mineral species, trinepheline (NaAlSiO4) and fabriesite
(Na3Al3Si3O12 center dot 2H(2)O), are described from late-stage
metamorphic veins of the jadeite deposit of Tawmaw-Hpakant (Myanmar).
Both minerals and their names were approved by the IMA Commission on New
Minerals and Mineral Names (IMA 2012-024 and IMA 2012-080). The name
trinepheline is known in literature for the polymorphs of synthetic
NaAlSiO4 with a value of the c parameter that is three times that of
nepheline. Fabriesite is named in memory of Jacques Fabrie's
(1932-2000), former professor of the ``Museum National d'Histoire
Naturelle{''} in Paris (France). Fabriesite and trinepheline occur
intimately intergrown together with nepheline, more rarely with albite
and other feldspar-group phases such as banalsite and stronalsite; other
associated minerals are jadeite and secondary products like natrolite
and harmotome. All phases have been identified via electron backscatter
diffraction (EBSD) patterns. Both fabriesite and trinepheline are
pseudomorph after jadeite and occur as skeletal allotriomorphic crystals
up to 15-20 mu m long and 5-10 mu m wide. They are white to yellowish in
hand specimen, colourless in thin section; the streak is white and the
lustre appears vitreous to greasy; they are non-fluorescent; Mohs'
hardness is 5-51/2. Empirical formulae (EMPA analysis) are very close to
the ideal compositions with traces of Ca and K for trinepheline, and of
Ca, K, Ba, Mg, Fe, and Mn for fabriesite. Calculated densities are 2.642
g cm(-3) for trinepheline (space group P6(1), a = 9.995 angstrom, c =
24.797 angstrom) and 2.386 g cm(-3) for fabriesite (space group Pna2(1),
a = 16.426 angstrom, b = 15.014 angstrom, c = 5.223 angstrom),
respectively. The strongest five lines in the calculated X-ray powder
diffraction patterns {[}d (angstrom) (I)(hkl)] are: 3.163(100)(122),
3.834(81)(023), 4.133(49)(006), 3.272(40)(120) and 2.403(31)(127) for
trinepheline; 3.41(100)(240), 4.41(77)(201), 2.97(70)(421),
2.61(40)(002) and 8.21(36)(200) for fabriesite.