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Peatite-(Y) and ramikite-(Y), two new Na-Li-Y+ or -Zr phosphate-carbonate minerals from the Poudrette Pegmatite, Mont Saint-Hilaire, Quebec

Andrew M. McDonald, Malcolm E. Back, Robert A. Gault and Laszlo Horvath
Peatite-(Y) and ramikite-(Y), two new Na-Li-Y+ or -Zr phosphate-carbonate minerals from the Poudrette Pegmatite, Mont Saint-Hilaire, Quebec
The Canadian Mineralogist (August 2013) 51 (4): 569-596

Abstract

Peatite-(Y), Li (sub 4) Na1 (sub 2) (Y,Na,Ca,HREE) (sub 12) (PO (sub 4) ) (sub 12) (CO (sub 3) ) (sub 4) (F,OH) (sub 8) , and ramikite-(Y), Li (sub 4) Na (sub 12) (Y,Ca,HREE) (sub 6) Zr (sub 6) (PO (sub 4) ) (sub 12) (CO (sub 3) ) (sub 4) O (sub 4) (OH,F) (sub 4) , are two new minerals discovered in the core of the Poudrette pegmatite at Mont Saint-Hilaire, Quebec. Epitactic-like, euhedral crystals (pseudocubes) of both minerals range from 0.1 to 1 mm in size (average: 0.2 mm), with ramikite-(Y) forming yellowish-white cores (dominant) and peatite-(Y) occurring as thin (< 50 um) pale pink rims. Crystals of peatite-(Y) exhibit the dominant forms pinacoid {100}, {010}, and {001} and the minor forms rhombic prism {110}, {101}, and {011}, with crystals of ramikite-(Y) showing the possible forms pedion {100},{001}, {010}, {010}, {001}, and {001}. The most common associated minerals include albite, rhodochrosite, siderite, chabazite-Na, synchysite-(Ce), and sabinaite. Peatite-(Y) displays a brittle fracture with very good {100}, {010}, and {001} cleavages; ramikite-(Y) has a splintery fracture with possible weak to poor {100}, {010}, and {001} cleavages. Peatite-(Y) has a vitreous luster and ramikite-(Y) has a vitreous to dull luster. Both minerals have a white streak and neither shows any discernible fluorescence under long-, medium-, or short-wave ultraviolet radiation. Both minerals have an approximate Mohs hardness of 3. Peatite-(Y) has a calculated density of 3.62(1) g/cm (super 3) and ramikite-(Y) of 3.60(1) g/cm (super 3) . Both minerals have a very low birefringence (approximately 100), exhibit parallel extinction, and give poor interference figures; the optic sign and measured 2V of both are unknown. Only one refractive index for each could be measured: peatite-(Y), beta = 1.601(1) and for ramikite-(Y), beta = 1.636 (1). Four analyses of peatite-(Y) gave an average (range) of (wt. %): Li (sub 2) O 1.96 (calc.), Na (sub 2) O 12.95 (12.50-13.30), CaO 1.15 (0.98-1.51), Y (sub 2) O (sub 3) 37.32 (37.01-37.52), Gd (sub 2) O (sub 3) 0.61 (0.54-0.74), Dy (sub 2) O (sub 3) 3.08 (2.91-3.44), Ho (sub 2) O (sub 3) 0.67 (b.d.-1.02), Er (sub 2) O (sub 3) 2.88 (2.59-3.15), Tm (sub 2) O (sub 3) 0.28 (b.d.-0.40), Yb (sub 2) O (sub 3) 1.78 (1.67-1.92), ZrO (sub 2) 0.67 (0.63-0.70), ThO (sub 2) 0.37 (b.d.-0.56), P (sub 2) O (sub 5) 27.29 (27.09-27.64), F 4.35 (4.03-4.62), CO (sub 2) 5.79 (calc.), H (sub 2) O 0.31 (calc.), O = F -1.83, total 99.75, corresponding to Li (sub 4) Na (sub 12) (Y (sub 10.06) Na (sub 0.72) Ca (sub 0.62) Dy (sub 0.50) Er (sub 0.46) Yb (sub 0.28) Zr (sub 0 .17) Ho (sub 0.11) Gd (sub 0.10) Tm (sub 0.04) Th (sub 0.04) Tb (sub 0.02) ) (sub Sigma 13.12) (PO (sub 4) ) (sub 11.70) (CO (sub 3) ) (sub 4) [F (sub 6.97) (OH) (sub 1.03) ] (sub Sigma 8) and the simplified formula, Li (sub 4) Na (sub 12) (Y,Na,Ca,HREE) (sub 12) (PO (sub 4) ) (sub 12) (CO (sub 3) ) (sub 4) (F,OH) (sub 8) . For ramikite-(Y), 22 analyses gave an average (range) of (wt. %): Li (sub 2) O 2.01 (calc.), Na (sub 2) O 11.25 (10.32-13.34), CaO 4.15 (4.01-4.27), Y (sub 2) O (sub 3) 16.48 (14.88-18.25), La (sub 2) O (sub 3) 0.11 (b.d.-0.48), Ce (sub 2) O (sub 3) 0.10 (b.d.-0.40), Nd (sub 2) O (sub 3) 0.08 (b.d.-031), Dy (sub 2) O (sub 3) 1.11 (0.96-1.23), Er (sub 2) O (sub 3) 1.18 (1.01-1.36), Yb (sub 2) O (sub 3) 0.57 (0.46-0.68), ZrO (sub 2) 23.40 (22.66-24.70), ThO (sub 2) 0.49 (b.d.-0.70), HfO (sub 2) 0.69 (0.48-0.92), Al (sub 2) O (sub 3) 0.14 (0.09-0.22), P (sub 2) O (sub 5) 28.10 (27.47-28.58), F 0.62 (0.24-0.90), CO (sub 2) 5.92 (calc.), H (sub 2) O 0.92 (calc.), O = F -0.26, total 97.06, corresponding to Li (sub 4) (Na (sub 10.79) Ca (sub 1.21) ) (sub Sigma 12) (Y (sub 4.34) Ca (sub 0.99) Dy (sub 0.18) Er (sub 0.18 ) Yb (sub 0.09) La (sub 0.02) Ce (sub 0.02) Nd (sub 0.01) ) (sub Sigma 5.83) (Zr (sub 5.65) Hf (sub 0.10) Th (sub 0.06) ) (sub Sigma 5.81) [(P (sub 0.98) Al (sub 0.01) ) (sub Sigma 0.99) O (sub 4) ] (sub 12) (CO (sub 3) ) (sub 4) O (sub 4) [(OH) (sub 3.03) F (sub 0.97) ] (sub Sigma 4.00) and the simplified formula, Li (sub 4) (Na,Ca) (sub 12) (Y,Ca,HREE) (sub 6) Zr (sub 6) (PO (sub 4) ) (sub 12) (CO (sub 3) ) (sub 4) O (sub 4) (OH,F) (sub 4) . In both peatite-(Y) and ramikite-(Y), the presence of Li (sub 2) O was confirmed via crystal-structure and LAM-ICP-MS analyses and both H (sub 2) O and CO (sub 2) via results of crystal-structure, infrared, and Raman analyses. Peatite-(Y) crystallizes in space group P222 with a 11.167(2), b 11.164(2), c 11.162(2) Aa, V 1391.7(1) Aa (super 3) , and Z = 1, and ramikite-(Y) in space group P1 with a 10.9977(6), b 10.9985(6), c 10.9966(6) Aa, alpha 90.075(4), beta 89.984(4), gamma 89.969(4) degrees , V 1330.1(1) Aa (super 3) , and Z = 1. The strongest six lines on the X-ray powder-diffraction pattern [d in Aa (I) (hkl)] for peatite-(Y) are: 4.56(57)(211,121,112), 3.95(57)(220,202,022), 3.54(46) (310,301,130), 2.99(83)(321,312,231), 2.63(100)(330,303,033), 2.149(42)(333) and for ramikite-(Y): 11.04(76)( 010, 100, 001), 7.80(79)( 011, 110,101), 6.36(75) (111, 111, 111, 111), 3.89(100)( 022, 220,202), 2.94(98) (132, 123, 231), 2.59(98)( 033,330,303). The crystal structure of peatite-(Y) was refined to R = 3.37% and wR (sub 2) = 9.36% for 3816 reflections and that of ramikite-(Y) to R = 5.13% and wR (sub 2) = 13.06% for 8272 reflections. While not strictly isostructural, both minerals have similar crystal structures dominated by M (sub phi 8) polyhedra (M = Y,Zr; phi = unspecified ligand). These are linked into six-membered, edge- or corner-sharing clusters, which in turn are joined together by PO (sub 4) tetrahedra. Both LiO (sub 6) octahedra and CO (sub 3) groups are positioned within the corner-sharing clusters. Linkages among all these polyhedra produce an open, equidimensional framework structure, with Na occupying the resulting cavities. Although possessing complex crystal structures, both minerals may be considered more simply as homeotypes of body-centered cubic Fe (or CsCl) or, alternatively, as complex derivatives of cation-deficient perovskite-related structures. Both minerals are late-stage products, possibly related to the in situ alteration of the pre-existing mineral assemblage (dawsonite, burbankite-group minerals, sabinaite, muscovite-polylithionite, etc.) present in the core of the Poudrette pegmatite.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 51
Serial Issue: 4
Title: Peatite-(Y) and ramikite-(Y), two new Na-Li-Y+ or -Zr phosphate-carbonate minerals from the Poudrette Pegmatite, Mont Saint-Hilaire, Quebec
Affiliation: Laurentian University, Department of Earth Sciences, Sudbury, ON, Canada
Pages: 569-596
Published: 201308
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 24
Accession Number: 2014-004230
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 8 tables
N45°15'00" - N45°34'60", W73°19'60" - W72°49'60"
Secondary Affiliation: Royal Ontario Museum Toronto, CAN, CanadaCanadian Museum of Nature, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201404
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