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Identity HelpUnknown Norway
9th Jul 2012 15:38 UTCTorben Kjeldgård
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
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
9th Jul 2012 16:32 UTCDonald Peck
9th Jul 2012 17:35 UTCRonald John Gyllenhammer Expert
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
Peter
9th Jul 2012 21:06 UTCTorben Kjeldgård
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
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
13th Jul 2012 10:54 UTCSpencer Ivan Mather
13th Jul 2012 13:40 UTCTorben Kjeldgård
Do HCl affect hydrotalcite? if it does I think I will buy this one.
Torben
13th Jul 2012 16:23 UTCKnut Edvard Larsen 🌟 Manager
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
good luck with the testing,
regards,
stephanie :-)
13th Jul 2012 19:59 UTCTorben Kjeldgård
When you touch the rock, it leaves a white powder on your fingers.
Torben
13th Jul 2012 22:28 UTCRonald John Gyllenhammer Expert
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
And a closer look at the white stuff.
Torben
29th Jul 2012 03:40 UTCAnonymous User
29th Jul 2012 04:26 UTCJosé Zendrera 🌟 Manager
29th Jul 2012 08:25 UTCTorben Kjeldgård
It has no fluorescence under UV. And it is not any mica.
Regards
Torben
29th Jul 2012 08:32 UTCAnonymous User
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