Canadian Rockhound: Normandite

Normandite
Abstracted by Robert Gault

Normandite, ideally NaCa(Mn,Fe)(Ti,Nb,Zr)Si₂O₇OF is a newly described mineral species from the Poudrette Quarry, Mont Saint-Hilaire, Quebec and is the Ti-analogue of låvenite. It was formerly designated as UK 59. The mineral was originally discovered by Charles Normand in 1980 in miarolitic cavities in nepheline syenite associated with albite, kupletskite, natrolite and donnayite-(Y). It was found again in 1986 in nepheline syenite and since then has been found frequently but in minor quantities indicating that it is often overlooked and is more abundant than first thought. A mineral with similar physical properties and chemical composition has been found in Russia at Partachorr, Khibina massif, Kola Peninsula and near the Koklukhtiuai and Muruai Rivers, Lovozero massif, Kola Peninsula, at Tamazeght, Haut Atlas, Morocco and at Tenerife, Canary Islands.

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); 2V_calc. = 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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