Beforsit
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
- Brazil :
-
People's Republic of China :
- Bayan Obo , Inner Mongolia
- Weishan
- Germany :
- Gabon :
- India :
- Canada :
- Kenya :
- Malawi :
-
Namibia :
- Eureka , Damaraland
- Marinkas Kwela
- Ondurukurume , Damaraland
-
Paraguay :
- Sapucai (Siliko-Beforsit)
- Russia :
-
Sweden :
- Bergeforsen near the island of Alnön (type locality)
- Råsta near Sundsvall
-
South Africa :
- Glenover , Limpopo
- Nooitgedacht -Magmatite Complex
- Phalaborwa , Limpopo
- Tanzania :
Individual evidence
- ^ 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 .