Ludwigite from Central Sweden: New Data and Crystal Structure Refinement

P. W. U. Appel1 and M. F. Brigatti2
1 Geological Survey of Denmark and Greenland, Thoravej 8, DK-2400 NV, Copenhagen, Denmark
2 Dipartimento di Scienze della Terra, Università di Modena, Largo S. Eufemia 19, I-41100, Modena, Italy

Abstract: Ludwigite from B-bearing iron ores in the Bergslagen area of central Sweden and in the coastal area north of Stockholm has been studied using chemical and single-crystal diffraction techniques. Structure refinements, completed for three crystals showing slightly different Al contents, in the space group Pbam (agreement factor: 2.42 ⩽ R ⩽ 2.79) indicate that: (1) octahedral M1, M2 and M3 bond distances are similar, although the calculated site population suggests that M1 and M2 are nearly completely occupied by Mg whereas M3 also contains Fe2+ and Fe3+; (2) in the M4 octahedron Fe3+ and Al dominate over Mg (and Fe2+); and (3) the distortion parameter, BLD, indicates that M3 is the most regular, whereas M4 is the most distorted octahedron.

Keywords: ludwigite • Tallgruvan • Sweden • borates • chemistry • structure refinement

Mineralogical Magazine; August 1999 v. 63; no. 4; p. 511-518; DOI: 10.1180/002646199548682
© 1999, The Mineralogical Society
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