The structure of acuminite, a strontium aluminium fluoride mineral

• Published in: Zeitschrift für Kristallographie - Crystalline Materials
• Other Authors: Andersen, E. Krogh, Ploug-Sørensen, G., Leonardsen, E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Walter de Gruyter GmbH 1991
• Subjects: Inorganic Chemistry; Condensed Matter Physics; General Materials Science; Greenland
• Online Access: http://dx.doi.org/10.1524/zkri.1991.194.3-4.221; https://www.degruyter.com/document/doi/10.1524/zkri.1991.194.3-4.221/xml; https://www.degruyter.com/document/doi/10.1524/zkri.1991.194.3-4.221/pdf

Abstract An X-ray diffraction study of single crystals of acuminite, a strontium aluminium fluoride mineral from Ivigtut, Greenland [SrAlF 4 (OH) · H 2 O, a = 13.223(1) Å, b = 5.175(1) Å, c = 14.251(1) Å, β = 111.61(2), C 2/ c , Z = 8, D m = 3.295 g cm −3 , D c = 3.305 g cm −3 ] used 2138 diffraction intensities (CAD-4 diffractometer), and was refined to R (unweighted) = 0.069. The strontium ions are 9-coordinated to 7 fluoride ions and 2 water molecules, the aluminium ions have octahedral coordination, 4 fluoride ions and 2 hydroxyl ions. The structure of acuminite is compared with the structure of tikhoenkovite another modification of SrAlF 4 (OH) · H 2 O.