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Oddities from Brandberg, Namibia
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Mike Wood




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PostPosted: Jan 14, 2015 18:38    Post subject: Re: Oddities from Brandberg, Namibia  

Incredibly clear and sharp photo's of the quartz Pierre!
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PostPosted: Jan 14, 2015 19:19    Post subject: Re: Oddities from Brandberg, Namibia  

Excellent photos Pierre!
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PostPosted: Jan 15, 2015 04:22    Post subject: Re: Oddities from Brandberg, Namibia  

Hello Pierre

Don't you mean 'negative crystals', rather than 'inverted crystals'? I think they form as the trapped solution cools and the dissolved silica crystallises on the inner walls of the host quartz, necessarily following the crystallographic structure and orienation of the host. The gas bubble forms as the gas too comes out of solution. Gentle heating can cause the gas to redissolve.

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PostPosted: Jan 15, 2015 07:10    Post subject: Re: Oddities from Brandberg, Namibia  

Likewise, Pierre, I have usually termed them negative crystal inclusions, but I suppose inverted works, although when I think of inverted it is as up-side-down, not out-side-in. It amazes me that these inclusions match perfectly the exterior geometry of the host crystal, but surely makes sense. It seems the Brandberg quartz is rich in very interesting inclusions. Am I wrong, or does quartz exhibit these negative - invert crystal forms more offen than most minerals?
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PostPosted: Jan 15, 2015 11:25    Post subject: Re: Oddities from Brandberg, Namibia  

xenolithos wrote:
Hello Pierre

Don't you mean 'negative crystals', rather than 'inverted crystals'? I think they form as the trapped solution cools and the dissolved silica crystallises on the inner walls of the host quartz, necessarily following the crystallographic structure and orienation of the host. The gas bubble forms as the gas too comes out of solution. Gentle heating can cause the gas to redissolve.

Duncan


Hi Duncan, I held the crystal and felt nothing negative, only positive energy! Only kidding! :-)
I looked up in the dictionary, inverted - 'put upside down or in the opposite position, order, or arrangement'. Just a question, why would some sections of the interior crystal form after the main crystal? I have seen water and air bubbles in some of these, clearly indicating that some, or all, are hollow. When you view broken crystals, the formations can be clearly seen. My guess is that these negative/inverted crystals form as a result of gas(H) trapped inside and that these form together with the main crystal.
Anyway, that is just my thought. Regards.

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PostPosted: Jan 15, 2015 11:43    Post subject: Re: Oddities from Brandberg, Namibia  

vic rzonca wrote:
Likewise, Pierre, I have usually termed them negative crystal inclusions, but I suppose inverted works, although when I think of inverted it is as up-side-down, not out-side-in. It amazes me that these inclusions match perfectly the exterior geometry of the host crystal, but surely makes sense. It seems the Brandberg quartz is rich in very interesting inclusions. Am I wrong, or does quartz exhibit these negative - invert crystal forms more offen than most minerals ?


Hi Vic. Looking at your specimens, it seems to me that the conditions under which they formed are fairly similar to that of the Brandberg area. I am sorry, I cannot answer your question.
How about a photo or two of some of your specimens with inverted crystals? Regards.



P1420764.JPG
 Mineral: Quartz
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 33 x 13 x 12 mm
 Description:
Quartz with inverted crystals. This crystal features in our collection. It has a story to it. In short, I gave this crystal to Riana not long after we met.
 Viewed:  10954 Time(s)

P1420764.JPG



P1420766.JPG
 Mineral: Quartz
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 33 x 13 x 12 mm
 Description:
Quartz with inverted crystals. Same as above.
 Viewed:  10965 Time(s)

P1420766.JPG



P1420785.JPG
 Mineral: Quartz
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 33 x 13 x 12 mm
 Description:
Quartz with inverted crystals. Same as above.
 Viewed:  10986 Time(s)

P1420785.JPG



P1420719.JPG
 Mineral: Quartz
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 33 x 13 x 12 mm
 Description:
Quartz with inverted crystals. Same as above.
 Viewed:  10956 Time(s)

P1420719.JPG



P1420724.JPG
 Mineral: Quartz
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 33 x 13 x 12 mm
 Description:
Quartz with inverted crystals. Same as above.
 Viewed:  10968 Time(s)

P1420724.JPG



P1420745.JPG
 Mineral: Quartz
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 33 x 13 x 12 mm
 Description:
Quartz with inverted crystals. Same as above.
 Viewed:  10980 Time(s)

P1420745.JPG



P1420747.JPG
 Mineral: Quartz
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 33 x 13 x 12 mm
 Description:
Quartz with inverted crystals. Same as above.
 Viewed:  10973 Time(s)

P1420747.JPG



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PostPosted: Jan 15, 2015 11:59    Post subject: Re: Oddities from Brandberg, Namibia  

I apologize, I missed the comments of Michael, Don, Mike and Gerard. Thank you very much! Regards.
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PostPosted: Jan 15, 2015 13:52    Post subject: Re: Oddities from Brandberg, Namibia  

Fascinating quartz and photos! Congratulations!
Probably I'm confused:
- Crystallographic orientations of host and negative crystals seem be different.
- In some photos seems as there is a 60º crossed striation, not usual on quartz.
Don't got it...

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PostPosted: Jan 15, 2015 14:09    Post subject: Re: Oddities from Brandberg, Namibia  

Josele wrote:
Fascinating quartz and photos! Congratulations!
Probably I'm confused:
- Crystallographic orientations of host and negative crystals seem be different.
- In some photos seems as there is a 60º crossed striation, not usual on quartz.
Don't got it...


Hi Josele. Thank you for your kind compliments. I do not mind if you use one or more of the photos to draw crystallographic diagrams to illustrate your point. I am afraid my knowledge here is insufficient. Best regards.

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PostPosted: Jan 15, 2015 15:04    Post subject: Re: Oddities from Brandberg, Namibia  

Pierre, also mine is insufficient. Maybe someone can help on this.
Negative crystal seem be tabular. Biggest faces seem be of the prism but I'm not sure. Perhaps they are r or z faces and that would explain the apparent different orientation.
That's all I can talk about.

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PostPosted: Jan 16, 2015 00:11    Post subject: Re: Oddities from Brandberg, Namibia  

Hello Pierre!

Excellent photos and the negative crystals are textbook examples! It seems that quartz shows such formations more frequently than other minerals, but this is also known from fluorite, calcite, galena (!), gypsum and others. I think it is not really clear what reasons are accountable for these negative crystals. One reason is, that crystals are grown fast and I think the temperature is also a reason, but I'm not sure - if I have some time, I will look in my library.

Martin

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PostPosted: Jan 16, 2015 03:56    Post subject: Re: Oddities from Brandberg, Namibia  

Martin Rich wrote:
Hello Pierre!

Excellent photos and the negative crystals are textbook examples! It seems that quartz shows such formations more frequently as other minerals, but this also known from fluorite, calcite, galenite (!), gypsum and others. I think it is not really clear what reasons are accountable for this negative crystals. One reason is, that crystals are grown fast and I think the temperature is also a reason, but I'm not sure - if I have some time, I will look in my library.

Martin


Hi Martin. Thank you for the compliment. I spent a few hours photographing these 2 specimens and discarded a few hundred photos! Maybe one day I will have a focus rail and a SLR camera with a Tamron lens:-) The growing conditions of the Brandberg quartz crystals were very harsh, so I can imagine that the crystals grew quickly. Any more info will be welcome. Regards.

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PostPosted: Jan 16, 2015 07:22    Post subject: Re: Oddities from Brandberg, Namibia  

Pierre

Great photos and it is great to see the negative crystals so clearly.

Thank you

James
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PostPosted: Jan 16, 2015 09:01    Post subject: Re: Oddities from Brandberg, Namibia  

James wrote:
Pierre

Great photos and it is great to see the negative crystals so clearly.

Thank you

James


Thank you James! I would love to have Peter's opinion on this. Regards.

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PostPosted: Jan 22, 2015 04:17    Post subject: Re: Oddities from Brandberg, Namibia  

The crystallographic orientation of a negative crystal is the same as the host crystal. The only difference that is seen in your pictures being the unequal development of facets (but each facet of the negative crystal remains strictly parallel to the host crystal facets)
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PostPosted: Feb 03, 2015 02:17    Post subject: Re: Oddities from Brandberg, Namibia  

Whoa, that's cool. Excellent photos!
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PostPosted: Feb 03, 2015 04:22    Post subject: Re: Oddities from Brandberg, Namibia  

Tiffany7mo wrote:
Whoa that's cool. Excellent photos!


Thanks Tiffany!

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PostPosted: Jul 30, 2015 11:25    Post subject: Re: Oddities from Brandberg, Namibia  

Fake specimens (or doctored specimens) are a rarity from Brandberg, so I consider them as 'oddities'.
A while ago, we purchased some mineral specimens from a friend. When he showed us some matrix amethyst crystal specimens, he said that he thought that they may have been glued onto the matrix. We purchased them anyway and later on I studied them carefully. I found 4 that have been glued on basalt matrix and covered expertly with very small calcite crystals. The only 'give away' was an unusual sheen on the calcite, suggesting glue. Whoever did this, knows his job. I placed 2 of the specimens in pool acid which removed the crystals from their matrix. The calcite dissolved leaving only a lump of, what looks like epoxy. I am keeping the 2 remaining specimens intact as rare samples of 'doctored' Brandberg specimens. Meanwhile, we are working to trace the culprit/s and will warn them to discontinue their trade or we will report them to the Namibian mine authorities.



P1070846.JPG
 Mineral: Quartz (variety quartz amethyst)
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 51 x 45 x 36 mm
 Description:
One of the 2 specimens left intact (an art work of deception)
 Viewed:  8650 Time(s)

P1070846.JPG



P1070851.JPG
 Mineral: Quartz (variety quartz amethyst)
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 51 x 45 x 36 mm
 Description:
Same specimen as above, with a close up showing the 'cover up'.
 Viewed:  8650 Time(s)

P1070851.JPG



P1070854.JPG
 Mineral: Quartz (variety quartz amethyst)
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 66 x 42 x 36 mm
 Description:
Specimen 2, also left intact as a piece of 'craft' (in order to deceive).
 Viewed:  8659 Time(s)

P1070854.JPG



P1070858.JPG
 Mineral: Quartz (variety quartz amethyst)
 Locality:
Brandberg area, Erongo Region, Namibia
 Dimensions: 66 x 42 x 36 mm
 Description:
A close up of the last crystal's 'cover up' job.
 Viewed:  8672 Time(s)

P1070858.JPG



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PostPosted: Jul 30, 2015 11:49    Post subject: Re: Oddities from Brandberg, Namibia  

The first two fake specimens that was exposed in the acid bath. I must stress that 'doctored' specimens from Namibia, and especially from Brandberg area, are rare. These are the fiirst we have ever encountered.


P1050504.JPG
 Mineral: Amethyst quartz crystal.
 Description:
This was what was left of the first specimen after being left in the acid for a while.
 Viewed:  8669 Time(s)

P1050504.JPG



P1050507.JPG
 Description:
The above specimens's crystal with glue which secured it to the matrix.
 Viewed:  8654 Time(s)

P1050507.JPG



P1050511.JPG
 Description:
The above one close up.
 Viewed:  8656 Time(s)

P1050511.JPG



P1050518.JPG
 Description:
The second one that experienced the acid bath. This photo was taken after a while in the acid.
 Viewed:  8670 Time(s)

P1050518.JPG



P1050526.JPG
 Description:
Finally, the crystal with glue.
 Viewed:  8663 Time(s)

P1050526.JPG



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PostPosted: Jul 30, 2015 16:46    Post subject: Re: Oddities from Brandberg, Namibia  

Beautiful amythest crystals Pierre, shame about the glue. I must say your photo's are extremely clear and well composed. Thanks for taking the trouble to photograph and post these glued specimens.

Best regards,
Mike

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