Lulzacite, Sr2Fe2+(Fe2+,Mg)(2)Al-4(PO4)(4)(OH)(10), a new strontium phosphate (Saint-Aubin-des-Chateaux, Loire-Atlantique, France).

Lulzacite, Sr2Fe2+(Fe2+,Mg)(2)Al-4 (PO4)(4)(OH)(10), is a new mineral from Ordovician quartzites at Saint-Aubin-des-Chateaux (Loire-Atlantique, France ). It occurs in veins of quartz and siderite, with pyrite, apatite and goya zite. Greyish-green colour; Mohs hardness: 5.5-6. Optically biaxial negativ e: n(p) = 1.654, n(m) = 1.674 and n(g) = 1.684. Distinctly pleochroic: brow n-yellow to light blue-violet. Triclinic P (1) over bar, a = 5.457(1), b = 9.131(2), c = 9.769(2) Angstrom, alpha = 108.47(3)degrees, beta = 91.72(3)d egrees, gamma = 97.44(3)degrees, V = 456.5(2) Angstrom(3), Z = 1. Strongest X-ray diffraction lines (d (Angstrom), I-obs, hkl): 4.47 (41, 02 (1) over bar), 3.591 (50, 111), 3.218 (100, 1 (2) over bar 2), 3.132 (62, 120), 3.02 6 (56, 12 (2) over bar), 2.878 (42, 03 (2) over bar), 2.812 (62, 11 (3) ove r bar), 2.653 (44, 1 (3) over bar 2), 2.634 (43, 023). D-mes = 3.55, D-calc = 3.58. Electron probe microanalysis (wt. %): SrO 21.79, BaO 1.20, FeO 16. 13, MgO 2.97, Al2O3 19.16, P2O5 28.50, V2O5 0.64, H2O (TGA) 10.29; total = 100.68%. Structural formula (according to the crystal structure) : (Sr0.96B a0.04)(2)Fe2+(Fe0.632+Mg0.37)(2)Al-4[(P0.98V0.02)O-4](4)(OH)(10); ideally: Sr2Fe2+(Fe2+,Mg)(2)Al-4(PO4)(4)(OH)(10). Isotypic with jamesite (lead arsen ate). Named in honour of Y. Lulzac, a ho discovered the species. (C) 2000 A cademie des sciences / Editions scientifiques et medicales Elsevier SAS.