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

FMF English Forum is moderated by John S. White and Peter Megaw
 

Spanish message board






Newest topics and users posts
24 Jun-20:26:48 Re: don lum collection (Don Lum)
24 Jun-20:22:29 Re: collection of richard & jensa arseneau (Richard Arseneau)
23 Jun-17:28:53 Re: collection of michael shaw (Crosstimber)
23 Jun-16:11:20 The mizunaka collection - quartz (Am Mizunaka)
23 Jun-14:55:20 Re: collection of michael shaw (Don Lum)
23 Jun-14:02:34 Re: new generation for picture - ploum (Ploum)
23 Jun-11:30:23 Re: collection of michael shaw (Crosstimber)
23 Jun-08:59:08 Re: collecting quartz on the little falls dolostone (Vic Rzonca)
23 Jun-06:26:55 Re: franjungle collection (Firmo Espinar)
23 Jun-01:19:20 Re: new generation for picture - ploum (Ploum)
22 Jun-14:09:13 Sainte-marie-aux-mines 2019 - it's already here (Jordi Fabre)
21 Jun-17:26:16 Re: amethyst and...? (Linus)
21 Jun-15:29:17 Re: collection of annemieke en rob schnerr (Rob Schnerr)
21 Jun-14:23:22 Re: don lum collection (Don Lum)
21 Jun-12:30:25 Re: collection of annemieke en rob schnerr (Rob Schnerr)
21 Jun-02:09:18 The mizunaka collection - quartz (Am Mizunaka)
21 Jun-01:35:49 Re: collection of annemieke en rob schnerr (Tobi)
20 Jun-18:28:18 Re: locality question regarding moroccan calcite (Tar4ntula)
20 Jun-11:18:33 Re: amethyst and...? (Mathias)
20 Jun-07:01:55 Re: collection of annemieke en rob schnerr (Rob Schnerr)
20 Jun-04:30:00 Re: a potpourri of musings....barely related to minerals. (Alfredo)
19 Jun-20:48:46 Re: fake ruby? (John Betts)
19 Jun-20:20:29 Re: cleaning nifontovite (Linus)
19 Jun-20:00:35 Re: cleaning nifontovite (Peter Megaw)
19 Jun-16:17:25 Amethyst and...? (Linus)

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
56080


The time now is Jun 24, 2019 20:49

Search for a textSearch for a text   

A general guide for using the Forum with some rules and tips
Quartz and Humboldtine? from Colombia
  
  Index -> Minerals and Mineralogy
Like
12


View previous topic :: View next topic  
Author Message

John Rakovan




Joined: 25 Mar 2014
Posts: 7
Location: Dept. of Geology, Miami University, Oxford, Ohio

View user's profile

Send private message

PostPosted: Oct 06, 2018 07:56    Post subject: Quartz and Humboldtine? from Colombia  

Colorless quartz crystals that are heavily included at their terminations with a vivid yellow material have recently appeared on the specimen market ( https://www.mindat.org/photo-875255.html ). We have been working to identify the yellow inclusions and first reported them to be humboldtine. We now believe that to be incorrect.

Early attempts to isolate yellow fibers from within the quartz or to identify them via Raman spectroscopy were unsuccessful.

One specimen in our possession had yellow fibrous material exposed at its surface. This was used for powder X-ray diffraction (PXRD) on a Bruker Quest (Mo K-alpha). The data give an excellent match with humboldtine.

Later, fibers from inside a quartz crystal were isolated. These give no discernable X-ray diffraction pattern. Multiple XRD datasets from included material reveal only quartz, which must be admixed with some of the fiber samples.

If the fibers are X-ray amorphous, this would explain why the first PXRD data shows only humboldtine. An admixture of humboldtine with an amorphous material will only yield diffraction peaks for humboldtine.

Another quartz sample exhibited a small area coated with a druse of tiny, sharp, equant, yellow crystals. PXRD data from these also match humboldtine.

We speculate that the surface humboldtine taken from the two samples described above is a product of cleaning with oxalic acid. Iron staining (iron oxides) on quartz can be effectively removed by soaking in Oxalic acid. This is a common practice in cleaning quartz specimens. Dissolved iron can then combine with oxalic acid C2H2O4 to form humboldtine Fe2+(C2O4) · 2H2O if the samples are not adequately rinsed.

Further study of the yellow fibrous inclusions is ongoing.

John Rakovan, Miami University



2327 3.jpg
 Description:
 Viewed:  3026 Time(s)

2327 3.jpg


Back to top
Reply to topic Reply with quote
Like
6
   

lluis




Joined: 17 Nov 2006
Posts: 618

View user's profile

Send private message

PostPosted: Oct 06, 2018 08:10    Post subject: Re: Quartz and Humboldtine? from Colombia  

Hi, John

Thanks for all info!

Being chemist myself, and cleaning minerals, I think that what you say is just what happened: a badly cleaned iron stained quartz... (that is as many ones I have seen...)

With best wishes

Lluís
Back to top
Reply to topic Reply with quote
Like
   

Bob Harman




Joined: 06 Nov 2015
Posts: 544
Location: Indiana


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Oct 06, 2018 10:41    Post subject: Re: Quartz and Humboldtine? from Colombia  

JOHN, As you know there were several of these examples in Denver. The best were VERY pricey. Are you saying there might be intentional partial cleaning of iron staining with an intention to deceive? BOB
Back to top
Reply to topic Reply with quote
Like
   

alfredo
Site Admin



Joined: 30 Jan 2008
Posts: 736


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Oct 06, 2018 11:46    Post subject: Re: Quartz and Humboldtine? from Colombia  

There are undoubtedly more "minerals" around that were the accidental result of cleaning procedures, and some of them have even wangled their way through the IMA approval procedure and become "approved species".

A few years ago I noticed some tiny colorless tourmaline-like rods on fumarolic hematite from Argentina. The crystals turned out to be lead citrate, the result of attempts by local Argentines to remove ugly white anglesite crusts with citric acid, and these crystals only narrowly avoided getting submitted to the IMA as a potential new species, but they did at least result in an interesting journal paper (by Tony Kampf) because they were a new structure type.
Back to top
Reply to topic Reply with quote
Like
   

John Rakovan




Joined: 25 Mar 2014
Posts: 7
Location: Dept. of Geology, Miami University, Oxford, Ohio

View user's profile

Send private message

PostPosted: Oct 06, 2018 14:24    Post subject: Re: Quartz and Humboldtine? from Colombia  

Bob Harman wrote:
JOHN, As you know there were several of these examples in Denver. The best were VERY pricey. Are you saying there might be intentional partial cleaning of iron staining with an intention to deceive? BOB


Hi Bob,

No, this is not at all what I am saying. I don’t think there has been any attempt to deceive. These are natural specimens. I have seen photos of them in situ.

The yellow fibrous inclusions which make the specimens so beautiful are all natural. In many cases they are completely encased in the quartz and could not be affected by cleaning. What I am saying is that our original identification of what the fibers are is incorrect. We do not yet know what they are. We do know that they are not humboldtine.

Cheers,

John
Back to top
Reply to topic Reply with quote
Like
   

Bob Harman




Joined: 06 Nov 2015
Posts: 544
Location: Indiana


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Oct 06, 2018 14:36    Post subject: Re: Quartz and Humboldtine? from Colombia  

OKAY! That should adequately explain it to both Lluis and me. BOB
Back to top
Reply to topic Reply with quote
Like
   

Fiebre Verde




Joined: 11 Sep 2013
Posts: 833
Location: Paris Area


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Oct 06, 2018 15:06    Post subject: Re: Quartz and Humboldtine? from Colombia  

Then what is not natural is the Columbia part of the story.
Columbia is (sometimes) the fake word for Colombia.
(nothing personal John - this is a VERY interesting thread :-) )
Gérard

All fixed Gérard.
Michael
Back to top
Reply to topic Reply with quote
Like
1
   

Jordi Fabre
Overall coordinator of the Forum



Joined: 07 Aug 2006
Posts: 4289
Location: Barcelona


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Oct 06, 2018 16:43    Post subject: Re: Quartz and Humboldtine? from Colombia  

Thanks a lot John, very useful.

I'm taking off the word Humboldtine from all the "Mineral" boxes because they are "institutional" boxes and of course not from the FMFers' texts that should be always strongly respected.
Back to top
Reply to topic Reply with quote
Like
   

marco campos-venuti




Joined: 09 Apr 2014
Posts: 192
Location: Sevilla


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Oct 07, 2018 12:20    Post subject: Re: Quartz and Humboldtine? from Colombia  

I bought this in 2006, supposedly from Brazil. It looks so similar!
Here the yellow appears to be inside. The vermicular growth reminds me of chlorite family minerals. The yellow is brighter in real life than in the pictures. Is it a different thing?



Imagen1.jpg
 Mineral: Quartz
 Locality:
Brazil
 Dimensions: 3 cm
 Description:
 Viewed:  2705 Time(s)

Imagen1.jpg



Imagen2.jpg
 Mineral: Quartz
 Locality:
Brazil
 Dimensions: 3 cm
 Description:
 Viewed:  2714 Time(s)

Imagen2.jpg


Back to top
Reply to topic Reply with quote
Like
2
   

John Rakovan




Joined: 25 Mar 2014
Posts: 7
Location: Dept. of Geology, Miami University, Oxford, Ohio

View user's profile

Send private message

PostPosted: Oct 12, 2018 09:42    Post subject: Re: Quartz and Humboldtine? from Colombia  

Hi Marco,

The habit of the inclusions in the Columbian quartz is distinctly different. It does not look at all vermicular as do the inclusions in your sample.

Cheers,

John

marco campos-venuti wrote:
I bought this in 2006, supposedly from Brazil. It looks so similar!
Here the yellow appears to be inside. The vermicular growth reminds me of chlorite family minerals. The yellow is brighter in real life than in the pictures. Is it a different thing?
Back to top
Reply to topic Reply with quote
Like
   

Bob Harman




Joined: 06 Nov 2015
Posts: 544
Location: Indiana


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: May 12, 2019 01:08    Post subject: Re: Quartz and Humboldtine? from Colombia  

The current issue of R & M periodical (vol 94 #3, May-June 2019) has an article by John Rakovan and David Ziga on these very interesting Colombian quartz specimens.

David Ziga had a wonderful display case devoted exclusively to these specimens at the recent Cincinnati mineral show. In fact, his case won an award at the show.
Unfortunately, I did not photograph his case; perhaps John R or another follower of this forum might have taken a picture of the case? It was quite an impressive display. BOB
Back to top
Reply to topic Reply with quote
Like
   

John Rakovan




Joined: 25 Mar 2014
Posts: 7
Location: Dept. of Geology, Miami University, Oxford, Ohio

View user's profile

Send private message

PostPosted: May 12, 2019 06:50    Post subject: Re: Quartz and Humboldtine? from Colombia  

Bob, here is a photo of the display at the 2019 Cincinnati Geofair


59746088_1045693835625569_133001410441641984_o.jpg
 Description:
Display at the 2019 Cincinnati Geofair
 Viewed:  964 Time(s)

59746088_1045693835625569_133001410441641984_o.jpg


Back to top
Reply to topic Reply with quote
Like
3
   

Bob Harman




Joined: 06 Nov 2015
Posts: 544
Location: Indiana


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: May 12, 2019 07:20    Post subject: Re: Quartz and Humboldtine? from Colombia  

PERFECT !! Regards and thanks John, BOB
Back to top
Reply to topic Reply with quote
Like
   

Fiebre Verde




Joined: 11 Sep 2013
Posts: 833
Location: Paris Area


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: May 12, 2019 09:40    Post subject: Re: Quartz and Humboldtine? from Colombia  

Bob Harman wrote:
The current issue of R & M periodical (vol 94 #3, May-June 2019) has an article by John Rakovan and David Ziga on these very interesting Colombian quartz specimens.

David Ziga had a wonderful display case devoted exclusively to these specimens at the recent Cincinnati mineral show. In fact, his case won an award at the show.
Unfortunately, I did not photograph his case; perhaps John R or another follower of this forum might have taken a picture of the case? It was quite an impressive display. BOB

Hi Bob
I have no access to that R & M issue.
Does the article explain what’s causing the yellowish/brownish color?
Gerard
Back to top
Reply to topic Reply with quote
Like
   

Bob Harman




Joined: 06 Nov 2015
Posts: 544
Location: Indiana


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: May 12, 2019 11:37    Post subject: Re: Quartz and Humboldtine? from Colombia  

Fiebre,

I am not a geologist so John R would be able to say more on this subject. Reread his original posting above on this subject.

However, from the article and what little I know, the answer is very complex and elusive. The yellowish color occurs mostly in fibers within the crystals rather than on the surface. Surface yellowish coloration, mostly due to iron oxides, has been ruled out, but its removal also posses a problem as when oxalic acid is used to remove the iron oxides, this seems to also affect the internal fibers in question, apparently forming humboldtine! . Humboldtine for the internal fibers was the early consideration, but is now suspected to be incorrect, except that testing after cleaning, repeatedly shows some alteration back to the humbodltine. The intimately admixed quartz fibers also interfere with testing, with various assays identifying only quartz.

All this is beyond me so other folks will have to add to this and explain more clearly. Bob
Back to top
Reply to topic Reply with quote
Like
   

Fiebre Verde




Joined: 11 Sep 2013
Posts: 833
Location: Paris Area


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: May 12, 2019 14:43    Post subject: Re: Quartz and Humboldtine? from Colombia  

Bob Harman wrote:
Fiebre,

I am not a geologist so John R would be able to say more on this subject. Reread his original posting above on this subject.

However, from the article and what little I know, the answer is very complex and elusive. The yellowish color occurs mostly in fibers within the crystals rather than on the surface. Surface yellowish coloration, mostly due to iron oxides, has been ruled out, but its removal also posses a problem as when oxalic acid is used to remove the iron oxides, this seems to also affect the internal fibers in question, apparently forming humboldtine! . Humboldtine for the internal fibers was the early consideration, but is now suspected to be incorrect, except that testing after cleaning, repeatedly shows some alteration back to the humbodltine. The intimately admixed quartz fibers also interfere with testing, with various assays identifying only quartz.

All this is beyond me so other folks will have to add to this and explain more clearly. Bob

Thanks for the reply Bob.
Then I guess the nature of these fibers is still under investigation.
Hopefully John R. will come up with an answer in the future.
Gerard
Back to top
Reply to topic Reply with quote
Like
   

GregC12345




Joined: 15 Jan 2018
Posts: 4
Location: California

View user's profile

Send private message

PostPosted: Jun 02, 2019 13:36    Post subject: Re: Quartz and Humboldtine? from Colombia  

Very interesting information, and much appreciated as all of you appear to have admittedly much more knowledge of the subject than I do. I recently bought a single crystal of the aforementioned quartz with the yellow inclusion. Has there by chance been any update or new information uncovered about what this is (rare or otherwise)? - Greg
Back to top
Reply to topic Reply with quote
Like
   
Display posts from previous:   
   Index -> Minerals and Mineralogy   All times are GMT - 5 Hours
Page 1 of 1
    

 
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 2006-2019


Powered by FMF