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Identity HelpUnknown Norway

9th Jul 2012 15:38 UTCTorben Kjeldgård

This specimen is white as you can see, has a hardness about 3 has a micaeous look, white streak, milky and pearly colour,

some kind of white mica? it comes of in flakes. has a chalky feel. Any ideas?

NB I have just tried with HCA so it is most likely Calcite or aragonite.

Regards

Torben

9th Jul 2012 15:56 UTCRonald John Gyllenhammer Expert

Hi Torben,

Which area is this from? Is it near Granåsen deposit, Mosjøen, Vefsn, Nordland? Possibly Brucite. We'll see what others think.

Ron

9th Jul 2012 16:11 UTCTorben Kjeldgård

It is from Vrådal, not a known locality, They are preparing for a new golfcourse, and it is found there.

9th Jul 2012 16:32 UTCDonald Peck

Brucite seems to fit, as Ron pointed out. Can you try to dissolve a bit of it in HCl. Brucite should dissolve. Then if you have any barium chloride solution, a few drops in a slightly acid solution should precipitate barium sulfate, dense and white.

9th Jul 2012 17:35 UTCRonald John Gyllenhammer Expert

Hi Torben,

I am unfamilar with the geology of the Vrådal area but I do know the area has a variety of some very old rock units. I think the Vrådal area hosts granites, metavolcanics, metasedimentary rocks and gneisses. Just what units outcrop where you found this specimen, I can't tell you. Brucite may be possible if found in some altered layers of marble but again I don't if any units of this nature outcrop there. Don offerred some sound advise on testing for Brucite and perhaps others here are possibly more familar with the local geology can contribute to the discussion. You might also seek some advice locally from a mineral club or a university. Good luck to you and all the best.

Ron

9th Jul 2012 19:36 UTCPeter Andresen Expert

Have you ruled out calcite? It would been my first thought - hydrothermal veins and fracture fillings with calcite, and sometimes fluorite are kown from the area, but not brucite.

Peter

9th Jul 2012 21:06 UTCTorben Kjeldgård

have found Flourite on other specimens, Calcite is also a good guess, but the pearly and the micaeous appearance, do confuse me.

It is very much looking like the inside of a seashell. But no marble on matrix, only some other layers that look like chalcedony.

Torben

9th Jul 2012 21:56 UTCRonald John Gyllenhammer Expert

Hi Torben,

The only other idea I have on this would be possibly something like Talc or Hydrotalcite. Talc does occur elsewhere within Telemark.

Ron

13th Jul 2012 05:48 UTCJenna Mast

It looks similar to I specimen I received from a dealer in Denmark that was labeled wollastonite from Greenland. I know there are deposits in Finland though I don't know about Norway. Wollastonite is not a carbonate...it has an Si atom in there, but it can be associated with carbonates.

13th Jul 2012 10:54 UTCSpencer Ivan Mather

Hydrotalcite is found in the Vradal area, so I would suggest that your specimen is this.

13th Jul 2012 13:40 UTCTorben Kjeldgård

Thanks for the help.

Do HCl affect hydrotalcite? if it does I think I will buy this one.

Torben

13th Jul 2012 16:23 UTCKnut Edvard Larsen 🌟 Manager

Looking at the photo alone i would have guessed of calcite perhaps together with some clay mineral ( smectite) .

Torben:

What exact was the reaction when you used HCl ? If it's calcite it would be an reaction like seen here: http://www.youtube.com/watch?v=OXxyrcPdmpA

Generally when trying to identifiy minerals one of the first rules are to examine the matrix ( if possible)- they can tell about the chemical environment the mineral was found in;-) . Certain minerals just occurs in certain kind of rocks etc. Hydrotalcite occurs (in Norway) always in serpentine rocks ( Snarum, Sannidal), Wollastonite ( in Norway always in contact metamorphic skarn rocks especially in the Oslo Area). None of these rocks are as far as i know known from Vrådal in Telemark.

Torben, could you please describe more the matrix. Perhaps this will help you..

Common rocks around Vrådal hyttegrend and the Golf course are belonging to the Vrådal pluton ( granites ). Could your specimen (look on the backside) be granitic ?

Spencer said:

"Hydrotalcite is found in the Vradal area". I am very interested to hear more about that find. So far as I know there is not registered any confirmed finds of hydrotalcite in the Vrådal area.

13th Jul 2012 18:29 UTCStephanie Martin

The pearly lustre and foliation reminds me of anthophyllite, although the hardness does not seem to fit.

good luck with the testing,

regards,

stephanie :-)

13th Jul 2012 19:59 UTCTorben Kjeldgård

The matrix is granite. I have seen a lot of calcite, but not someone like this, it fuss with HCl

When you touch the rock, it leaves a white powder on your fingers.

Torben

13th Jul 2012 22:28 UTCRonald John Gyllenhammer Expert

Hi Torben,

Please excuse me but just to clear up a bit of confusion on my part, you said, "...it fuss with HCl". Did you mean to say that it will "fizz with HCl"? If so, I think we can narrow this down at least to a carbonate.

Massive Magnesite can look a bit like this, it will also most times effervesce in HCl, better so when the HCl is warm or the Magnesite is powdered. Magnesite can appear at times under different conditions to be both pearly and porcelainous or even sometimes chalky, all characteristics you have described. The hardness would also somewhat fit your description. You might also check for fluorescence if you can.

I think it would be a good idea to post some more well focused closeup images if you have time. For me, this does not look like granite. I'm sure better images would help.

Regards,

Ron

14th Jul 2012 16:09 UTCTorben Kjeldgård

Backside of specimen

And a closer look at the white stuff.

Torben

29th Jul 2012 03:40 UTCAnonymous User

i think at massive pectolite but the hardness seem to low. have you check this sample under uv lamp since your last message .

29th Jul 2012 04:26 UTCJosé Zendrera 🌟 Manager

Seems to have very good cleavage, perhaps muscovite or any other mica?

29th Jul 2012 08:25 UTCTorben Kjeldgård

Hi

It has no fluorescence under UV. And it is not any mica.

Regards

Torben

29th Jul 2012 08:32 UTCAnonymous User

maybe something like white cookeite but i dont know if it's possible from this locality

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