Si-rich bergslagite from a granitic pegmatite at Tennvatn, north Norway

Autor(en)

Gunnar Raade, Uwe Kolitsch, Thomas A Husdal

Abstrakt

Si-rich bergslagite from an amazonite-cleavelandite pegmatite at Tennvatn in Sørfold, Nordland, north Norway, has the empirical composition Ca1Ca1.00Ca2 Ca0.068(Be0.94Si0.06)(As0.774 Si0.226)O4[(OH)0.97O0.03], based on a single-crystal structure refinement (MoKa radiation, CCD area detector, 293 K, space group P21/c, a = 4.878(1), b = 7.810(2), c = 10.130(2) A°, ß = 90.09(3)°, V = 385.92 (15) A°3, Z = 4, R1(F) = 4.48%) and electron-microprobe analyses of Ca, As and Si. The structure refinement revealed the presence of a previously unknown, partially occupied and octahedrally coordinated Ca2 site that provides charge-balance compensation. The sample has the highest content of Si ever reported in bergslagite, and can be compared to (As0.87Si0.08) found in bergslagite from the type locality (Ln°gban, Sweden). The results also indicate that the previously postulated OH substitution scheme in type bergslagite is erroneous. Substantial substitution of Si for As in arsenates and arsenosilicates seems to be relatively rare; some examples are discussed.

Organisation(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

University of Oslo

Journal

GFF

Band

128

Seiten

65-68

Anzahl der Seiten

4

ISSN

1103-5897

Publikationsdatum

2006

Peer-reviewed

Ja

ÖFOS 2012

105113 Kristallographie, 105116 Mineralogie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/ecfd4214-5ccf-4861-b36e-0804fa510786