Beforsit

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Magnesiocarbonatite from the Verity Paradise Carbonatite Complex in British Columbia, Canada. The handpiece is 75 millimeters wide.

Beforsit is an igneous rock belonging to the rock group of carbonatites . Together with rauhaugite , it belongs to the dolomite carbonatites , as its modal mineral composition is dominated by dolomite .

Etymology and type locality

The rock name Beforsit comes from its type locality , Bergeforsen near Alnön , Västernorrland in Sweden .

Initial description

Beforsit was scientifically described for the first time in 1928 by H. von Eckermann.

mineralogy

The main mineral in Beforsit is by definition dolomite, which is represented with more than 50 percent by volume. The dolomite can also be partially replaced by anchorite (such as in the dolomitic-anchoritic beforsites of Schelingen in the Kaiserstuhl ) or, rarely, by magnesite . Accompanying minerals are usually apatite , barite , magnetite , sodium- rich orthoclase , titanite , biotite , quartz and sulfide minerals , more rarely also melilite and riebeckite . Cavities in the rock can be filled with carbon dioxide .

Chemical composition

Weight% Beforsit from the Alnö complex
SiO 2 6.12
TiO 2 0.68
Al 2 O 3 1.31
Fe 2 O 3 6.94
MnO 0.75
MgO 12.75
CaO 29.03
Na 2 O 0.14
K 2 O 0.79
P 2 O 5 2.66
CO 2 37.03
BaO 0.11
SrO 0.0.10

Occur

Beforsite usually occurs as medium to fine-grained dike rock .

Varieties

  • Apatite-Beforsit
  • Barite-Beforsit
  • Biotite-Beforsit
  • Feldspar beforsit
  • Magnetite beforsite
  • Biotite-melilithite-beforsite
  • Quartz Beforsit
  • Picrite basalt -Beforsit (with olivine -Pseudomorphosen)
  • Riebeckit-Beforsit

Occurrence

The carbonatite of Sukulu in Uganda

Individual evidence

  1. ^ H. von Eckermann: Dikes belonging to the Alnö formation in the cuttings of the East Coast Railway . In: Geologiska Föreningens i Stockholm Förhandlingar, Stockholm . Vol. 50, 1928, pp. 381-412 .