from Mont Saint-Hilaire, Quebec
Ottawa-Carleton Geoscience Centre, Department of Earth Sciences,
Carleton University, Ottawa , Ontario K1S 5B6
Research Division, Canadian Museum of Nature,
Ottawa , Ontario K1P 6P4
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ABSTRACT
Normandite, the titanium analogue of låvenite, is a new mineral species from the Poudrette quarry, Mont Saint-Hilaire, Quebec. It is found in nepheline syenite and in miarolitic cavities in nepheline syenite, associated with nepheline, albite, microcline, aegirine, natrolite, catapleiite, kupletskite, eudialyte, cancrinite, villiaumite, rinkite, and donnayite-(Y).
It occurs as transparent to translucent orange-brown aggregates of subparallel acicular crystals up to 10 mm in length, and as patches of yellow, fibrous crystals. It has a white to very pale yellow streak and vitreous luster. It is brittle, with distinct {100} and {001} cleavages, and a conchoidal fracture. Normandite is biaxial negative, with indices of refraction a 1.743 (2), b 1.785 (2), and g 1.810 (5), 2V meas. in the range 72-84°, 2V calc. = 74° and a moderate dispersion r > v. Pleochroism is pronounced: X pale yellow, Y yellow, Z brownish red to deep red. The optical orientation is Y = b, X ^ c = 15° (in obtuse angle b). Normandite is monoclinic, space group P21/a, with a 10.828 (7), b 9.790 (7), c 7.054 (2) Å, b108.20 (3)°, V 709.9 (8) Å3 and Z = 4. The strongest six lines of the
X-ray powder-diffraction pattern [d in Å (I)(hkl)] are:
2.859 (100)(122)
The crystals are elongate on {001} and flattened on {010}, with the following forms, in order of predominance: {100}, {110} and {001}. Electron-microprobe analyses gave:
(9.10-9.40)
(0.01-0.02)
(15.08-15.59)
(9.11-9.52)
(5.89-6.26)
(17.09-17.83)
(3.51-4.61)
(2.29-2.73)
(31.69-32.04)
(4.82-5.31)
The empirical formula based on 9(O + F) is:
Na1.12Ca1.03(Mn0.49Fe0.32)S0.81 (Ti0.82Nb0.11Zr0.08)S1.01
Si2.00O7.99F1.01, ideally NaCa(Mn,Fe)(Ti,Nb,Zr)Si2O7OF.
D meas. = 3.50 (1), Dcalc. = 3.48 g/cm3. The name honors Charles Normand, who discovered the species.
Keywords: normandite, new mineral species, Ti-analogue of låvenite, Mont Saint-Hilaire, Quebec.
The Canadian Mineralogist