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Normandite Abstracted by Robert Gault
In miarolitic cavities, normandite occurs as groups of fine acicular crystals up to 2 mm in length and as irregular fibrous patches, whereas in nepheline syenite it occurs as euhedral, prismatic crystals up to 10 mm in length and as groups of sub-parallel acicular crystals and fine fibres. It is generally orange to orange-brown to yellow in fine fibres and is translucent to transparent, with a vitreous lustre. It is non-fluorescent. The crystals are elongate along [001] and flattened on {100} with (100) and (110) faces commonly striated along their length. It has distinct {100} and {001} cleavages and a conchoidal fracture. It is brittle with a hardness of 5 (Mohs scale). The calculated density is 3.48 g/cm3. It is biaxial negative with indices of refraction a 1.743(2), b = 1.785(2) and g = 1.810(5); 2Vcalc. = 74º. Pleochroism is pronounced X pale yellow, Y yellow, Z brownish red to deep red. Normandite is monoclinic, space group P21/a, with a 10.828(7), b 9.790(7), c 7.054(2) Å, b 108.20(3)° , V 709.9(8) Å3 and Z = 4.
Source:Chao, G.Y. and Gault, R.A. 1997. Normandite, the Ti-analogue of låvenite from Mont Saint-Hilaire, Québec. Can. Min. 35:1035-1039.
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