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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
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.
| Description: |
Quartz with unknown inclusion.
Brandberg, Namibia
59 x 31 x 29 mm
The included crystal is approx. 15 mm long |
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47407 Time(s) |
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| Description: |
Quartz with unknown inclusion.
Brandberg, Namibia
59 x 31 x 29 mm |
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47418 Time(s) |
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| Description: |
Quartz with unknown inclusion.
Brandberg, Namibia
59 x 31 x 29 mm
Photo taken in artificial light. |
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47415 Time(s) |
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| Description: |
Unknown crystal
Brandberg, Namibia
Approx. 15 mm long |
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47406 Time(s) |
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| Description: |
Unknown crystal
Brandberg, Namibia
Approx. 15 mm long
Same as above |
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47439 Time(s) |
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| Description: |
Unknown crystal
Brandberg, Namibia
Approx. 15 mm long
Last 3 photos taken in sunlight. |
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47369 Time(s) |
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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: 262
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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
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
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.
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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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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
'The tree of silence bears the fruit of peace. ' |
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
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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Pierre Joubert
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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
Posts: 160
Location: Barcelona
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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
Posts: 1605
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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Pierre Joubert
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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.
| Description: |
| Brazil. 2,5 cm. (inclusion) |
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47235 Time(s) |
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| St. Gottard, Switzerland. 1.cm (edge) |
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47169 Time(s) |
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Lubudi, Congo
2 cm.
(a detail of the published image. |
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47214 Time(s) |
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47190 Time(s) |
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47193 Time(s) |
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| Description: |
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47235 Time(s) |
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
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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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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cascaillou
Joined: 27 Nov 2011
Posts: 262
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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
Posts: 1605
Location: Western Cape
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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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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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Debbie Woolf
Joined: 09 Feb 2009
Posts: 168
Location: Kent
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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
Posts: 1605
Location: Western Cape
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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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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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