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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Feb 23, 2014 13:53 Post subject: Oddities from Brandberg, Namibia |
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While cleaning crystals, I noted one damaged crystal with a most unusual included crystal. I assume, that as I have never seen something like this from Brandberg before, it must be a rarity from this area, especially the size. There are no similar crystals included. The 'unknown' crystal appears to be square (more flat than square). Any ideas would be welcome.
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Quartz with unknown inclusion. Brandberg, Namibia 59 x 31 x 29 mm The included crystal is approx. 15 mm long |
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Quartz with unknown inclusion. Brandberg, Namibia 59 x 31 x 29 mm |
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Quartz with unknown inclusion. Brandberg, Namibia 59 x 31 x 29 mm Photo taken in artificial light. |
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Unknown crystal Brandberg, Namibia Approx. 15 mm long |
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Unknown crystal Brandberg, Namibia Approx. 15 mm long Same as above |
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Unknown crystal Brandberg, Namibia Approx. 15 mm long Last 3 photos taken in sunlight. |
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_________________ Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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cascaillou
Joined: 27 Nov 2011
Posts: 250
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Posted: Feb 23, 2014 18:09 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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such inclusions have been reported in alpine quartz crystals, but their exact nature often remained uncertain. It was suggested that they were possibly anhydrite or scapolite, that was either pseudomorphosed (for instance by muscovite), or dissolved to leave a hollow tube (which might be stained by a thin inner coating)
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marvsT/Nminerals
Joined: 06 Nov 2008
Posts: 68
Location: Juda, Wisconsin
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Posted: Feb 24, 2014 00:32 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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Do you know what other associated minerals came out of that pocket or nearby pockets? The associated minerals might give you a clue as to the mineralogy of the immediate area. Marv
_________________ Member: Badger Lapidary and Geological Society
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Feb 24, 2014 01:17 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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cascaillou wrote: | such inclusions have been reported in alpine quartz crystals, but their exact nature often remained uncertain. It was suggested that they were possibly anhydrite or scapolite, that was either pseudomorphosed (for instance by muscovite), or dissolved to leave a hollow tube (which might be stained by a thin inner coating) |
Hi Cascaillou. I also considered the possibility that the original crystal dissolved and left a perfect cavity which in turn was filled with another mineral, possibly even clay. The small black bits of mineral could be either hematite or even epidote (more likely the first). This appears to be sitting directly on the surface of the strange included crystal.
_________________ Pierre Joubert
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Pierre Joubert
Joined: 09 Mar 2012
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Posted: Feb 24, 2014 01:25 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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marvsT/Nminerals wrote: | Do you know what other associated minerals came out of that pocket or nearby pockets? The associated minerals might give you a clue as to the mineralogy of the immediate area. Marv |
Hi Marv. The associated minerals common to this direct area are feldspar,calcite, prehnite, epidote, analcime, hematite(mostly as small inclusions). There are also other minerals but these are uncommon. Somewhere, I have a quartz crystal or two from this area that has a few small yellowish needle like inclusions. I must search for them; perhaps there is a link between the two.
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Feb 24, 2014 01:37 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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See a list of minerals from Mindat. https://www.mindat.org/loc-4534.html
The mineral specimens from Goboboseb rarely has more than 4 of these attached. The most common is calcite, prehnite, feldspar, epidote and analcime. Inclusions are usually small flakes of hematite, minute epidote crystals, or minute prehnite crystals.
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Carles Curto
Joined: 14 Sep 2006
Posts: 160
Location: Barcelona
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Posted: Feb 24, 2014 01:56 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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could it be metallic?
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Carles Curto
Joined: 14 Sep 2006
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Posted: Feb 24, 2014 02:08 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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Very probably it is anhydrite. It has been cited, as inclusion, in some Swiss quartzes.
As example, you can see pages 140-142 of the book: Hyrsl, J., Niedermayr, G. 2003. Magic world: inclusions in quartz. Bode Verlag.
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Feb 24, 2014 02:27 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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Carles Curto wrote: | Very probably it is anhydrite. It has been cited, as inclusion, in some Swiss quartzes.
As example, you can see pages 140-142 of the book: Hyrsl, J., Niedermayr, G. 2003. Magic world: inclusions in quartz. Bode Verlag. |
Hi Carles. Cascaillou shares your thoughts 'such inclusions have been reported in alpine quartz crystals, but their exact nature often remained uncertain'. Can this book be viewed on line? If indeed, do you have a link.? I see anydrite is the dehydrated form of Gypsum. This could easily dissolve, espescially if the one end is open (which is the case here). The cavity can then be filled. However way you look at it, it is a very unusual occurance at Goboboseb.
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Carles Curto
Joined: 14 Sep 2006
Posts: 160
Location: Barcelona
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Posted: Feb 24, 2014 03:51 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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I don't know if the book is on line (I suppose not).
Anhydrite, even considering it, genetically, a dehydrated form of gypsum, is a different species, with a very different structure (orthorhombic, very frequently with pseudotetragonal shape). I don't really know if, in your case, you have anhydrite crystals, empty geometric channels or a complete substitution by another mineral. (in fact we don't know if it is really anhydrite).
to be clearer, I add some images and the complete English text (the book was published in German-English) of Hyrsl and Niedermayr.
I hope Jaroslav and Gerhard excuse me the use of these images.
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Brazil. 2,5 cm. (inclusion) |
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St. Gottard, Switzerland. 1.cm (edge) |
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Lubudi, Congo 2 cm. (a detail of the published image. |
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Feb 24, 2014 04:18 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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Carles Curto wrote: | I don't know if the book is on line (I suppose not).
Anhydrite, even considering it, genetically, a dehydrated form of gypsum, is a different species, with a very different structure (orthorhombic, very frequently with pseudotetragonal shape). I don't really know if, in your case, you have anhydrite crystals, empty geometric channels or a complete substitution by another mineral. (in fact we don't know if it is really anhydrite).
to be clearer, I add some images and the complete English text (the book was published in German-English) of Hyrsl and Niedermayr.
I hope Jaroslav and Gerhard excuse me the use of these images. |
Fantastic information Carles. Thank you very much. In this case the void appears to be filled with clay. What an unusual occurance, especially from Brandberg (Goboboseb area)
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cascaillou
Joined: 27 Nov 2011
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Posted: Feb 24, 2014 04:33 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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My data is also from the same book.
At the beginning of the book (in the part dealing about fluid inclusions and hollow cavities), there's another paragraph about those tubes. It is explained that while anhydrite and scapolite have been idntified as inclusions in quartz, the nature of these hollow tubes wasn't confirmed for sure, but hypothesized to be anhydrite or scapolite casts (after dissolution)
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Pierre Joubert
Joined: 09 Mar 2012
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Posted: Feb 24, 2014 04:53 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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cascaillou wrote: | My data is also from the same book.
At the beginning of the book (in the part dealing about fluid inclusions and hollow cavities), there's another paragraph about those tubes. It is explained that while anhydrite and scapolite have been idntified as inclusions in quartz, the nature of these hollow tubes wasn't confirmed for sure, but hypothesized to be anhydrite or scapolite casts (after dissolution) |
Thanks Cascaillou. Any more info will be welcome.
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Debbie Woolf
Joined: 09 Feb 2009
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Posted: Feb 24, 2014 07:11 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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Hi Pierre
I've never seen anything like that in the crystals from the Goboboseb & I've looked at 1000s with a loupe, I get mesmerized by the inclusions :0) I've never seen Prehnite included either.
Nice crystal & a keeper.
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Pierre Joubert
Joined: 09 Mar 2012
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Posted: Feb 24, 2014 07:33 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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Debbie Woolf wrote: | Hi Pierre
I've never seen anything like that in the crystals from the Goboboseb & I've looked at 1000s with a loupe, I get mesmerized by the inclusions :0) I've never seen Prehnite included either.
Nice crystal & a keeper. |
Hi Debbie. This year has been a mad one, I would love to sit down some day and add to the thread on quartz inclusions. I hope to photograph some prehnite inclusions as well. My favourite is the perfect negative crystals. How they form is an absolute mystery. Thanks for your input:-)
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Debbie Woolf
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Posted: Feb 24, 2014 08:20 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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I look forward to seeing the photos someday.
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cascaillou
Joined: 27 Nov 2011
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Posted: Feb 24, 2014 14:50 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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Pierre, if you're interested in inclusions you will like:
Magic World: Inclusions in Quartz (by Jaroslav Hyrsl and Gerhard Niedermayr)
This book is only about inclusions in quartz
Photoatlas of Inclusions in Gemstones, 3 volumes (by Eduard J. Gubelin and John I. Koivula)
All three volumes are excellent, and each of these cover all kind of inclusions found in many different gemstones. But you might be first interested in the second volume which has 124 pages about inclusions in quartz.
The Microworld of Diamonds (by John I. Koivula)
This one is only about inclusions in diamonds
Keep those books in mind for your birthday!
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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Posted: Feb 25, 2014 00:48 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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cascaillou wrote: | Pierre, if you're interested in inclusions you will like:
Magic World: Inclusions in Quartz (by Jaroslav Hyrsl and Gerhard Niedermayr)
This book is only about inclusions in quartz
Photoatlas of Inclusions in Gemstones, 3 volumes (by Eduard J. Gubelin and John I. Koivula)
All three volumes are excellent, and each of these cover all kind of inclusions found in many different gemstones. But you might be first interested in the second volume which has 124 pages about inclusions in quartz.
The Microworld of Diamonds (by John I. Koivula)
This one is only about inclusions in diamonds
Keep those books in mind for your birthday! |
Hi Cascaillou. I am indeed interested in quartz inclusions (very much so). I will join a club just for that. I will keep the books in mind and see if I can order them somewhere Regards:-)
_________________ Pierre Joubert
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Pierre Joubert
Joined: 09 Mar 2012
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Posted: Apr 20, 2014 05:27 Post subject: Re: Unknown crystal in Brandberg quartz crystal |
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Hi Jordi. Is it possible to change the topic of this thread to' Oddities from Brandberg, Namibia'? This will allow me to show a few more different unusual minerals, most of which I do not know the identity of. By voorbaat dank!
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Jordi Fabre
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Posted: Apr 20, 2014 11:52 Post subject: Re: Oddities from Brandberg, Namibia |
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Pierre Joubert wrote: | Hi Jordi. Is it possible to change the topic of this thread to' Oddities from Brandberg, Namibia'? This will allow me to show a few more different unusual minerals, most of which I do not know the identity of. By voorbaat dank! |
Done!
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