We use cookies to show content based on your preferences. If you continue to browse you accept their use and installation. More information. >

FMF - Friends of Minerals Forum, discussion and message board
The place to share your mineralogical experiences


Spanish message board






Newest topics and users posts
28 Mar-09:37:50 Re: 2 unknowns co-occurring with caledonite, grand reef mine, az (Cfrench58)
27 Mar-19:47:08 Re: 2 unknowns co-occurring with caledonite, grand reef mine, az (Pete Richards)
27 Mar-16:15:44 Re: 2 unknowns co-occurring with caledonite, grand reef mine, az (Cfrench58)
27 Mar-15:18:59 Re: 2 unknowns co-occurring with caledonite, grand reef mine, az (Alfredo)
27 Mar-14:39:29 2 unknowns co-occurring with caledonite, grand reef mine, az (Cfrench58)
27 Mar-05:21:48 Re: the mim museum in beirut, lebanon (Mim Museum)
27 Mar-05:03:26 Re: trying to find information on rose/pink quartz and tourmaline associations. (Ning)
27 Mar-02:39:50 Re: the mim museum in beirut, lebanon (Tobi)
27 Mar-00:23:28 Re: collection of volkmar stingl (Volkmar Stingl)
26 Mar-00:53:41 Re: collection of volkmar stingl (Volkmar Stingl)
25 Mar-13:32:10 Re: collection of michael shaw (Michael Shaw)
25 Mar-00:25:58 The mizunaka collection - quartz (Am Mizunaka)
23 Mar-13:35:22 Re: collection of firmo espinar (Firmo Espinar)
22 Mar-08:32:28 Re: collection of michael shaw (Michael Shaw)
22 Mar-04:20:41 Re: the mim museum in beirut, lebanon (Mim Museum)
21 Mar-22:49:19 Re: green seam. Looks like it in a state of decay. (Ning)
21 Mar-22:47:40 Re: green seam. Looks like it in a state of decay. (Ning)
21 Mar-22:45:25 Re: green seam. Looks like it in a state of decay. (Ning)
21 Mar-15:34:23 Re: the mizunaka collection - quartz (Am Mizunaka)
21 Mar-14:35:08 Re: jim’s mineral collection (Jim Wilkinson)
21 Mar-14:15:36 The 4th phoenix heritage mineral show (phms) hosted by mineralogical society of arizona (m (Chris Whitney-smith)
21 Mar-04:36:10 Re: the mizunaka collection (Tobi)
21 Mar-04:11:47 Re: jim’s mineral collection (James Catmur)
20 Mar-23:34:15 The mizunaka collection - quartz (Am Mizunaka)
20 Mar-18:13:16 Re: jim’s mineral collection (Jim Wilkinson)

For lists of newest topics and postings click here


RSS RSS

View unanswered posts

Why and how to register

Index Index
 FAQFAQ RegisterRegister  Log inLog in
 {Forgotten your password?}Forgotten your password?  

Like
111802


The time now is Mar 28, 2024 17:28

Search for a textSearch for a text   

A general guide for using the Forum with some rules and tips
The information provided within this Forum about localities is only given to allow reference to them. Any visit to any of the localities requires you to obtain full permission and relevant information prior to your visit. FMF is strictly against any illicit activities related to collecting minerals.
Oddities from Brandberg, Namibia
  Goto page Previous  1, 2, 3, 4  Next
  Index -> Minerals and Mineralogy
Like
29


View previous topic :: View next topic  
Author Message

Mike Wood




Joined: 16 Dec 2010
Posts: 456
Location: Northern England


Access to the FMF Gallery title=

View user's profile

Send private message

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

Incredibly clear and sharp photo's of the quartz Pierre!
_________________
Rock basher
Back to top
Reply to topic Reply with quote
Like
   

Fiebre Verde




Joined: 11 Sep 2013
Posts: 942
Location: Paris Area


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 14, 2015 19:19    Post subject: Re: Oddities from Brandberg, Namibia  

Excellent photos Pierre!
Back to top
Reply to topic Reply with quote
Like
   

Duncan Miller




Joined: 25 Apr 2009
Posts: 138
Location: South Africa


Access to the FMF Gallery title=

View user's profile

Send private message

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.

Duncan
Back to top
Reply to topic Reply with quote
Like
   

vic rzonca




Joined: 18 Nov 2008
Posts: 820
Location: MA


Access to the FMF Gallery title=

View user's profile

Send private message

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?
Back to top
Reply to topic Reply with quote
Like
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

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.

_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

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:  22915 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:  22902 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:  22927 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:  22905 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:  22914 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:  22917 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:  22936 Time(s)

P1420747.JPG



_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
3
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

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.
_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
   

Josele




Joined: 10 Apr 2012
Posts: 405
Location: Tarifa, Spain


Access to the FMF Gallery title=

View user's profile

Send private message

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...

_________________
Josele
Back to top
Reply to topic Reply with quote
Like
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

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.

_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
   

Josele




Joined: 10 Apr 2012
Posts: 405
Location: Tarifa, Spain


Access to the FMF Gallery title=

View user's profile

Send private message

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.

_________________
Josele
Back to top
Reply to topic Reply with quote
Like
   

Martin Rich




Joined: 15 Aug 2013
Posts: 127
Location: Lower Austria


Access to the FMF Gallery title=

View user's profile

Send private message

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

_________________
We are living on the matrix.
Back to top
Reply to topic Reply with quote
Like
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

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.

_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
   

James Catmur
Site Admin



Joined: 14 Sep 2006
Posts: 1340
Location: Cambridge


Access to the FMF Gallery title=

View user's profile

Send private message

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
Back to top
Reply to topic Reply with quote
Like
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

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.

_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
   

cascaillou




Joined: 27 Nov 2011
Posts: 250

View user's profile

Send private message

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)
Back to top
Reply to topic Reply with quote
Like
   

Tiffany7mo




Joined: 02 Feb 2015
Posts: 1

View user's profile

Send private message

PostPosted: Feb 03, 2015 02:17    Post subject: Re: Oddities from Brandberg, Namibia  

Whoa, that's cool. Excellent photos!
Back to top
Reply to topic Reply with quote
Like
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Feb 03, 2015 04:22    Post subject: Re: Oddities from Brandberg, Namibia  

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


Thanks Tiffany!

_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

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:  20515 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:  20544 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:  20600 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:  20556 Time(s)

P1070858.JPG



_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
3
   

Pierre Joubert




Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape


Access to the FMF Gallery title=

View user's profile

Send private message

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:  20560 Time(s)

P1050504.JPG



P1050507.JPG
 Description:
The above specimens's crystal with glue which secured it to the matrix.
 Viewed:  20492 Time(s)

P1050507.JPG



P1050511.JPG
 Description:
The above one close up.
 Viewed:  20484 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:  20508 Time(s)

P1050518.JPG



P1050526.JPG
 Description:
Finally, the crystal with glue.
 Viewed:  20496 Time(s)

P1050526.JPG



_________________
Pierre Joubert


'The tree of silence bears the fruit of peace. '
Back to top
Reply to topic Reply with quote
Like
4
   

Mike Wood




Joined: 16 Dec 2010
Posts: 456
Location: Northern England


Access to the FMF Gallery title=

View user's profile

Send private message

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

_________________
Rock basher
Back to top
Reply to topic Reply with quote
Like
1
   
Display posts from previous:   
   Index -> Minerals and Mineralogy   All times are GMT - 5 Hours
Page 3 of 4
  Goto page Previous  1, 2, 3, 4  Next  

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


All pictures, text, design © Forum FMF 2006-2024


Powered by FMF