Sailaufite, (Ca, Na, 2Mn3O2(AsO42(CO3)-3H2O, a new mineral from Hartkoppe hill, Ober-Sailauf (Spessart mountains, Germany), and its relationship to mitridatite-group minerals and pararobertsite
- Author(s)
- Manfred Wildner, Ekkehart Tillmanns, Michael Andrut, Joachim Lorenz
- Abstract
Sailaufite, a new mineral with idealized composition CaNaMn3+3O2(AsO42(CO3)*3H2O, has been found at the locality Hartkoppe hill near Ober-Sailauf (Spessart mountains, Germany), associated with hausmannite, arseniosiderite, kutnahorite, dolomite, quartz, calcite, and Mn-calcite. It occurs as strongly intergrown, dark red-brown to black tabular crystals, often forming mammillated coatings on calcite and arseniosiderite. Mohs' hardness is ~3.5, the cleavage is perfect parallel (001), the tenacity is brittle with an uneven to conchoidal fracture. Crystals are optically biaxial negative, at 616 nm na = 1.757(5), ?ß.? = 0.004(1), 2V = 32(3)°, nß(calc) = 1.806, n?(calc) = 1.810. The strongest lines in the X-ray powder diffraction pattern are (dobs, I, hkl): 8.807, 100, 001; 5.654, 27, 130; 5.544, 17, 200; 2.936; 75, 003; 2.885, 19, 331; 2.816, 20, 332¯; 2.772, 36, 400; 2.514, 20, 133; 2.202, 55, 004. UV-VIS-IR spectroscopic measurements confirm the presence of AsO4 and CO3 groups as well as the absence of transition metal ions other than Mn3+ in sailaufite. The crystal structure of a small untwinned crystal fragment could be solved by direct methods from X-ray CCD data [monoclinic, space group Cm, a = 11.253(1), b = 19.628(1), c = 8.932(1) A°, ß = 100.05(1)°, Z = 6] and was refined on 8650 Fo2to wR2 = 0.079 and R1 = 0.045. The structure contains characteristics nonamer rings of edge-sharing Mn3+O6 octahedra forming compact pseudotrigonal [Mn3+9O6(AsO4) 6(CO3)3]9- sheets which are linked by layers composed of (Ca,Na,?)O5(H2O) 2 polyhedra and isolated water molecules. The octahedral nonamer rings correspond to those occuring in the Fe3+-phosphate mitridatite and bear strong similarities to the arrangement of Z-shaped octahedral chains in the Mn3+-phosphate pararobertsite.
- Organisation(s)
- Department of Mineralogy and Crystallography
- Journal
- European Journal of Mineralogy: an international journal of mineralogy, geochemistry and related sciences
- Volume
- 15
- Pages
- 555-564
- No. of pages
- 10
- ISSN
- 0935-1221
- DOI
- https://doi.org/10.1127/0935-1221/2003/0015-0555
- Publication date
- 2003
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1051 Geology, Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/sailaufite-ca-na-2mn3o2aso42co33h2o-a-new-mineral-from-hartkoppe-hill-obersailauf-spessart-mountains-germany-and-its-relationship-to-mitridatitegroup-minerals-and-pararobertsite(0868c3a1-4ea1-4c3b-844c-4d079952c494).html