Selsvitberget

DESCRIPTION

Selsvitberget is a pegmatite with a lot of Beryl. It was once mined for beryl and a total of about 2 ton were mined here.
The beryl quarry was closed down in the late 1960's.
Today the pegmatite quarry is abandoned, but there is a quarry for porphyr at the other side of the mountain. The porphyr is used in building roads and in asphalt because of it's great hardness.

GEOLOGY

The area around the pegmatite is dominated by granite rocks, and NE of it lies a porphyric dyke.
U-Pb analyses of columbite shows on a age of 1795 Ma for the pegmatite.
The pegmatite consists of a quartz vein with red microcline. It is exposed for about 80m long and a maximum width of 25m. The main part of the pegmatite consists of large blocky feldspar with pods of quartz. With the felspar comes sometimes large concentrations of well developed beryl crystals. The largest one reported were 2m long and about 25 cm in diameter.
There is also a number of other minerals in small amounts.
In a small area there is evidence on hydrothermal transformation of beryl into the secondary minerals of bertrandite, euclase and phenakite. Bertrandite is the most abundant mineral of the above mentioned, since it can replace whole beryl crystals. Up to 30 cm big masses of intergrown bertrandite have been found.
The other minerals occur more rarely, phenakite is often found as a border zone on euclas.

Visits

1997-10-14
This was the last mineral trip for the year. I visited Selsvitberget on my trip up to Umeå after my week in Bergslagen. I was driving after the instructions in Wilkes book, but since my german knowledge is a little out of date, I almost missed this quarry.
At first I didn't realize that Bollsta and Bollsta bruk is two different villages, It took me about an hour and help from one of the residents before I realized that! No wonder that there was a new lake in the reality....
When I reached the porphyric quarry the next problem arised... where is the old pegmatite, was it maybe gone ? I managed to walk two times around the main quarry, and was about to abandon the search when I finally found an old road. Following that I came to the lower part of the pegmatite and was able to climb along the dyke up to the quarry. On the way a number of small pieces of beryl showed me that I was on the right track.
After some digging around in the old quarry I found a crystal in the rock with nice form an undamaged, so I started to try to get it out.
To get it out meant that I had to remove about a 50 kg of quartz and feldspar, but it had some cracks that promised it to be possible to do.
About an hour later, I got one of the bigger rocks loose, and when I turn it around it shows me a nice beryl crystal, 6x4x30 cm. Unfortunately it is broken in three parts and the rest is still left in the mountain.
Now I realized that it had started to snow, so I took my findings and went down from the mountain, knowing that I will return in the summer.

Litterature

GFF 112:227
GFF 119:249
Nyttosten 1971.

Mineral assemblage

In the pegmatite :
Beryl, pyrite, arsenopyrite, chalcopyrite, bertrandite, euclase, phenakite, triplite, apatite, columbite, almandine, spessartine, microcline, flourite, chlorite, muscovite, biotite, quartz.
In the porphyr quarry :
Flourite, "porphyrite".

Beryl
Beryl in red microklin.
Collected 1997-10-14.
(300 dpi, 800x600, k)

Beryl
This is a prime example of the occurance of beryl at the Sels-Vitberget. The beryl is surrounded by red microcline and then quartz have filled up the remaining space in the pegmatite.
Collected 1997-10-14.
(300 dpi, 800x600, k)

Spessartine
Probably spessartine. The garnet have grown between two flakes of biotite and have only grown free in one direction.
Collected 1997-10-14.
(300 dpi, 800x600, k)

Possible bertrandite
There is a tiny crystal in the quartz at the center of the picture.
It might be bertrandite, but since it is so small, it is hard to do any precise measurements on it. The hardness seems to be slightly below quartz and the lustre is stronger than quartz.
The color is in a very weak nuance of yellow.
To check the crystalform I need a microscope, but I haven't had the time to do that check yet.
Collected 1997-10-14.
(300 dpi, 800x600, k)

Apatite
A piece of massive apatite together with red microkline.
The surface to the left shows a white color as a result of weathering.
Collected 1997-10-14.
(300 dpi, 800x600, k)

Apatite
The same rock as above, seen from the side.
Phosphate, hardness seems to be less than feldspar and higher than calcite. Scratched by steeltip and feldspar.
Soluble in weak HCl.
Collected 1997-10-14.
(300 dpi, 800x600, k)

If you have some questions, suggestions or comments you are welcome to write me a line or two.

Locality index. Main index.

axelsson@acc.umu.se

	Beryl Beryl in red microklin. Collected 1997-10-14. (300 dpi, 800x600, k)
	Beryl This is a prime example of the occurance of beryl at the Sels-Vitberget. The beryl is surrounded by red microcline and then quartz have filled up the remaining space in the pegmatite. Collected 1997-10-14. (300 dpi, 800x600, k)
	Spessartine Probably spessartine. The garnet have grown between two flakes of biotite and have only grown free in one direction. Collected 1997-10-14. (300 dpi, 800x600, k)
	Possible bertrandite There is a tiny crystal in the quartz at the center of the picture. It might be bertrandite, but since it is so small, it is hard to do any precise measurements on it. The hardness seems to be slightly below quartz and the lustre is stronger than quartz. The color is in a very weak nuance of yellow. To check the crystalform I need a microscope, but I haven't had the time to do that check yet. Collected 1997-10-14. (300 dpi, 800x600, k)
	Apatite A piece of massive apatite together with red microkline. The surface to the left shows a white color as a result of weathering. Collected 1997-10-14. (300 dpi, 800x600, k)
	Apatite The same rock as above, seen from the side. Phosphate, hardness seems to be less than feldspar and higher than calcite. Scratched by steeltip and feldspar. Soluble in weak HCl. Collected 1997-10-14. (300 dpi, 800x600, k)