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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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 Posted: Jan 15, 2015 11:43 Post subject: Re: Oddities from Brandberg, Namibia |
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| 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.
| Mineral: | Quartz |
| Locality: | | Brandberg area, Erongo Region, Namibia |  |
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| 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. |
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| Viewed: |
26765 Time(s) |
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| Mineral: | Quartz |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 33 x 13 x 12 mm |
| Description: |
| Quartz with inverted crystals. Same as above. |
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| Viewed: |
26766 Time(s) |
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| Mineral: | Quartz |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 33 x 13 x 12 mm |
| Description: |
| Quartz with inverted crystals. Same as above. |
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| Viewed: |
26801 Time(s) |
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| Mineral: | Quartz |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 33 x 13 x 12 mm |
| Description: |
| Quartz with inverted crystals. Same as above. |
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| Viewed: |
26773 Time(s) |
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| Mineral: | Quartz |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 33 x 13 x 12 mm |
| Description: |
| Quartz with inverted crystals. Same as above. |
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| Viewed: |
26772 Time(s) |
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| Mineral: | Quartz |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 33 x 13 x 12 mm |
| Description: |
| Quartz with inverted crystals. Same as above. |
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| Viewed: |
26773 Time(s) |
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| Mineral: | Quartz |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 33 x 13 x 12 mm |
| Description: |
| Quartz with inverted crystals. Same as above. |
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| Viewed: |
26808 Time(s) |
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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: Jan 15, 2015 11:59 Post subject: Re: Oddities from Brandberg, Namibia |
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I apologize, I missed the comments of Michael, Don, Mike and Gerard. Thank you very much! Regards.
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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
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| Posted: Jan 15, 2015 13:52 Post subject: Re: Oddities from Brandberg, Namibia |
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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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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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| Posted: Jan 15, 2015 14:09 Post subject: Re: Oddities from Brandberg, Namibia |
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| 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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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
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| Posted: Jan 15, 2015 15:04 Post subject: Re: Oddities from Brandberg, Namibia |
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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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Martin Rich
Joined: 15 Aug 2013
Posts: 127
Location: Lower Austria
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| Posted: Jan 16, 2015 00:11 Post subject: Re: Oddities from Brandberg, Namibia |
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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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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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| Posted: Jan 16, 2015 03:56 Post subject: Re: Oddities from Brandberg, Namibia |
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| 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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Pierre Joubert
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James Catmur
Site Admin
Joined: 14 Sep 2006
Posts: 1479
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| Posted: Jan 16, 2015 07:22 Post subject: Re: Oddities from Brandberg, Namibia |
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Pierre
Great photos and it is great to see the negative crystals so clearly.
Thank you
James
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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| Posted: Jan 16, 2015 09:01 Post subject: Re: Oddities from Brandberg, Namibia |
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| 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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Pierre Joubert
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cascaillou
Joined: 27 Nov 2011
Posts: 263
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| Posted: Jan 22, 2015 04:17 Post subject: Re: Oddities from Brandberg, Namibia |
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| 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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Tiffany7mo
Joined: 02 Feb 2015
Posts: 1
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| Posted: Feb 03, 2015 02:17 Post subject: Re: Oddities from Brandberg, Namibia |
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| Whoa, that's cool. Excellent photos!
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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| Posted: Feb 03, 2015 04:22 Post subject: Re: Oddities from Brandberg, Namibia |
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| Tiffany7mo wrote: | | Whoa that's cool. Excellent photos! |
Thanks Tiffany!
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Pierre Joubert
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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| Posted: Jul 30, 2015 11:25 Post subject: Re: Oddities from Brandberg, Namibia |
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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.
| Mineral: | Quartz (variety quartz amethyst) |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 51 x 45 x 36 mm |
| Description: |
| One of the 2 specimens left intact (an art work of deception) |
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| Viewed: |
24178 Time(s) |
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| Mineral: | Quartz (variety quartz amethyst) |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 51 x 45 x 36 mm |
| Description: |
| Same specimen as above, with a close up showing the 'cover up'. |
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| Viewed: |
24209 Time(s) |
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| Mineral: | Quartz (variety quartz amethyst) |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 66 x 42 x 36 mm |
| Description: |
| Specimen 2, also left intact as a piece of 'craft' (in order to deceive). |
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| Viewed: |
24260 Time(s) |
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| Mineral: | Quartz (variety quartz amethyst) |
| Locality: | | Brandberg area, Erongo Region, Namibia | |
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| Dimensions: | 66 x 42 x 36 mm |
| Description: |
| A close up of the last crystal's 'cover up' job. |
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| Viewed: |
24219 Time(s) |
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Pierre Joubert
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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| Posted: Jul 30, 2015 11:49 Post subject: Re: Oddities from Brandberg, Namibia |
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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.
| Mineral: | Amethyst quartz crystal. |
| Description: |
| This was what was left of the first specimen after being left in the acid for a while. |
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| Viewed: |
24227 Time(s) |
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| Description: |
| The above specimens's crystal with glue which secured it to the matrix. |
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| Viewed: |
24154 Time(s) |
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| Description: |
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| Viewed: |
24150 Time(s) |
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| Description: |
| The second one that experienced the acid bath. This photo was taken after a while in the acid. |
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| Viewed: |
24185 Time(s) |
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| Description: |
| Finally, the crystal with glue. |
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| Viewed: |
24170 Time(s) |
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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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Mike Wood
Joined: 16 Dec 2010
Posts: 456
Location: Northern England
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| Posted: Jul 30, 2015 16:46 Post subject: Re: Oddities from Brandberg, Namibia |
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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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