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
19 Oct-13:56:54 Re: collection of michael shaw (Crosstimber)
19 Oct-12:32:29 Re: collection of michael shaw (Tobi)
19 Oct-12:20:55 Re: franjungle collection (Tobi)
19 Oct-12:13:55 Re: alfredopetrovite (Tobi)
19 Oct-11:49:45 Re: collection of manuel mesa (Manuel Mesa)
19 Oct-11:17:09 Re: scepters - (1) (Marco Campos-venuti)
19 Oct-10:26:57 Re: scepters - (1) (Reef)
19 Oct-10:05:30 Re: alfredopetrovite (Alfredo)
19 Oct-07:59:39 Re: alfredopetrovite (John S. White)
19 Oct-07:51:37 Re: scepters - (1) (Marco Campos-venuti)
19 Oct-06:04:24 Re: scepters - (1) (Reef)
19 Oct-01:57:09 Re: alfredopetrovite (Pierre Joubert)
19 Oct-00:36:29 Re: 2015 tucson in retrospect (Robert Seitz)
18 Oct-22:57:24 Re: alfredopetrovite (Alfredo)
18 Oct-19:05:16 Re: franjungle collection (Franjungle)
18 Oct-16:19:49 Re: scepters - (1) (Steveb)
18 Oct-15:28:34 Re: munich show (mineralientage) 2017 (Jordi Fabre)
18 Oct-15:26:50 Re: 2015 tucson in retrospect (Don Lum)
18 Oct-14:53:13 Re: scepters - (1) (Reef)
18 Oct-13:42:02 Re: 2015 tucson in retrospect (Durgaprasadzone)
18 Oct-11:49:00 Re: collection of michael shaw (Crosstimber)
18 Oct-05:56:10 Re: collection of manuel mesa (Manuel Mesa)
17 Oct-17:46:51 The mizunaka collection - quartz (Am Mizunaka)
17 Oct-15:59:29 Re: new generation for picture - ploum (Ploum)
17 Oct-11:15:39 Re: collection of manuel mesa (Manuel Mesa)

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
33934


The time now is Oct 19, 2017 15:02

Search for a textSearch for a text   

A general guide for using the Forum with some rules and tips
Cechite from Ulldemolins
  
  Index -> Minerals and Mineralogy
Like
15


View previous topic :: View next topic  
Author Message

Cesar M. Salvan
Site Admin



Joined: 09 Jun 2008
Posts: 105
Location: Alcalá de Henares


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 26, 2016 20:37    Post subject: Cechite from Ulldemolins  

Cechite is a rare lead-iron vanadate, first described in samples from Alexander mine and the Posepny vein, at Vrancice (Bohemia, Czech Republic) Apart of the scarcity of the mineral, it is not very interesting for collectors (apart of systematic collectors), because it normally occurs as small granular masses or very small, black or dark brown, equant crystals. It's easily confused with goethite when massive and with mottramite or descloizite when it forms crystals. Probably some occurrences have been overlooked due to these similarities.

Cechite gained interest with the finding of very good crystals at the Santiago Mine (María Magdalena Mine), in Ulldemolins (Tarragona, Catalonia, Spain) by collectors from the GMC (Grup Mineralògic Catalá), where it forms well-formed euhedral crystals, usually on fluorite, forming beautiful specimens (for the species).

This is a good opportunity to observe and describe the Raman spectrum of this mineral. Raman spectroscopy is the ideal technique for the fast, reliable and non-destructive identification of vanadates and arsenates of the descloizite-adelite group, even when it forms minute crystals, but the Raman spectrum of cechite was unknown.

I used the good cechite from Ulldemolins to study its spectrum and I decided to publish the result here to spread its spectrum as much described as possible, in order to aid in future identifications of the material. Also, I want to share an interesting feature of the cechite from Ulldemolins: the occurrence of copper-rich crystals, whose study, as far as I know, does not match with any described species. This suggests an interesting structural problem or even a new species.

I present the description here and maybe somebody could add to the discussion, identify mistakes or collaborate to further study the structure and the potential identification of the specie(s) present:

To see this column you have to click on this link or the image:




cechita localidad tipo.jpg
 Mineral: Cechite
 Locality:
Alexander Shaft, Vrančice, Příbram, Central Bohemia Region, Bohemia, Czech Republic
 Dimensions: FOV 1 mm
 Description:
Usual cechite from the type locality. Compare with the cechite from Ulldemolins.
 Viewed:  2721 Time(s)

cechita localidad tipo.jpg



2016-11-16 16-54-35 (C).jpg
 Mineral: Cechite
 Locality:
Magdalena Mine (Santiago Mine), Lo Fangar (Els Solans) / La Font del Metge, Ulldemolins, Comarca Priorat, Tarragona, Catalonia, Spain
 Dimensions: FOV 5 mm
 Description:
 Viewed:  2723 Time(s)

2016-11-16 16-54-35 (C).jpg


Back to top
Reply to topic Reply with quote
Like
5
   

Cesar M. Salvan
Site Admin



Joined: 09 Jun 2008
Posts: 105
Location: Alcalá de Henares


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 28, 2016 16:11    Post subject: Re: Cechite  

More images of the interesting cechite with the undefined copper phase (maybe a new mineral?) from Ulldemolins.

In the samples are also present the descloizite-mottramite series, which forms green, very small crystals.



cechite 2016-12-28 21-18-29 (C).jpg
 Mineral: Cechite
 Locality:
Magdalena Mine (Santiago Mine), Lo Fangar (Els Solans) / La Font del Metge, Ulldemolins, Comarca Priorat, Tarragona, Catalonia, Spain
 Dimensions: FOV 1.5 mm
 Description:
Cechite with copper.
 Viewed:  2567 Time(s)

cechite 2016-12-28 21-18-29 (C).jpg



2016-12-28 21-25-47 (C).jpg
 Mineral: Cechite
 Locality:
Magdalena Mine (Santiago Mine), Lo Fangar (Els Solans) / La Font del Metge, Ulldemolins, Comarca Priorat, Tarragona, Catalonia, Spain
 Dimensions: FOV 1.5 mm
 Description:
copper-rich cechite
 Viewed:  2577 Time(s)

2016-12-28 21-25-47 (C).jpg



2016-12-28 21-35-50 (C).jpg
 Mineral: Mottramite-Descloizite series
 Locality:
Magdalena Mine (Santiago Mine), Lo Fangar (Els Solans) / La Font del Metge, Ulldemolins, Comarca Priorat, Tarragona, Catalonia, Spain
 Dimensions: FOV 1mm
 Description:
 Viewed:  2581 Time(s)

2016-12-28 21-35-50 (C).jpg



descloizita-mottramita.jpg
 Mineral: Mottramite-Descloizite series
 Locality:
Magdalena Mine (Santiago Mine), Lo Fangar (Els Solans) / La Font del Metge, Ulldemolins, Comarca Priorat, Tarragona, Catalonia, Spain
 Dimensions: FOV 1 mm
 Description:
 Viewed:  2576 Time(s)

descloizita-mottramita.jpg


Back to top
Reply to topic Reply with quote
Like
4
   

Peter Lemkin




Joined: 18 Nov 2016
Posts: 44
Location: Prague

View user's profile

Send private message

PostPosted: Dec 29, 2016 01:55    Post subject: Re: Cechite  

Photo 2016-12-28 21-25-47 certainly shows nice xx. I've collected at Vrancice and seen specimens at local Czech shows, but they were always 'black-uglies' without any euhedral xxm to my memory. I'd have to go back to the Mineral Museum to see if they have anything better, but it is currently closed for renovation.
Back to top
Reply to topic Reply with quote
Like
   

Cesar M. Salvan
Site Admin



Joined: 09 Jun 2008
Posts: 105
Location: Alcalá de Henares


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 29, 2016 07:09    Post subject: Re: Cechite  

Peter Lemkin wrote:
Photo 2016-12-28 21-25-47 certainly shows nice xx. I've collected at Vrancice and seen specimens at local Czech shows, but they were always 'black-uglies' without any euhedral xxm to my memory. I'd have to go back to the Mineral Museum to see if they have anything better, but it is currently closed for renovation.


That's a good point. Indeed, I never saw the cechite in euhedral crystals until now. Always as massive, granular or as much equant or rounded, very small crystals. As far as I know, the cechite from Ulldemolins is the best occurrence for this mineral to date.

But, in the Ulldemolins deposit is the same, anyway: the actually pure cechite, very close to the ideal composition, also forms the usual "black uglies". The euhedral crystals always contains significant copper and shows evidence of an additional mineral phase. Maybe the cechite is just a coating? are there two phases present, as the Raman seems to show? The crystals actually require a deeper study, but in my opinion these crystals are not cechite sensu stricto. It seems to be cechite plus/on something undefined.



cechita ulldemolins copia.jpg
 Mineral: Cechite
 Locality:
Magdalena Mine (Santiago Mine), Lo Fangar (Els Solans) / La Font del Metge, Ulldemolins, Comarca Priorat, Tarragona, Catalonia, Spain
 Dimensions: FOV 4 mm
 Description:
As smaller the size of crystals and less well formed, closer to the cechite ideal composition.
 Viewed:  2484 Time(s)

cechita ulldemolins copia.jpg


Back to top
Reply to topic Reply with quote
Like
1
   

Jordi Fabre
Overall coordinator of the Forum



Joined: 07 Aug 2006
Posts: 3926
Location: Barcelona


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 29, 2016 13:10    Post subject: Re: Cechite  

Cesar M. Salvan wrote:
...It seems to be cechite plus/on something undefined.

Maybe former Sphalerite replaced / epimorphic (or coated) by Cechite?
Back to top
Reply to topic Reply with quote
Like
   

Cesar M. Salvan
Site Admin



Joined: 09 Jun 2008
Posts: 105
Location: Alcalá de Henares


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 30, 2016 05:55    Post subject: Re: Cechite  

Jordi Fabre wrote:
Cesar M. Salvan wrote:
...It seems to be cechite plus/on something undefined.

Maybe former Sphalerite replaced / epimorphic (or coated) by Cechite?


I don't think so. I have two hypotheses:

- A crystal of mottramite grown in iron-rich conditions. The iron induced structural changes leading to a shift of the vanadate bands in Raman respect mottramite. Given that a series cechite-mottramite is not possible, there was a phase transition and final stage of crystal growth was cechite. So, formally the crystals would be cechite-coated mottramite. The reversal, i.e. cechite growing incorporating copper until a phase transition, would be possible, but less probable.

- there is an undefined phase present, covered or altered to cechite. This is because I never saw so intense shifts due to substitution in a species.

Anyway, a deeper structural analysis of the crystals is necessary. I can't do it, because I do not have instrumentation for analysis of such small crystals.

Anyway, at collector's label effects, the label cechite for those crystals is incomplete and inaccurate.
Back to top
Reply to topic Reply with quote
Like
   

Joan Rosell




Joined: 10 Jul 2014
Posts: 2
Location: El Prat de Llobregat - Barcelona

View user's profile

Send private message

PostPosted: Jan 02, 2017 10:04    Post subject: Re: Cechite from Ulldemolins  

We started studies on the cechite in July 2015. The first analysis we made showed the presence of Cu in the SEM-EDS spectra. But we studied inside broken crystals. In those crystals, Cu was a thin layer on the surface (less than 20 um). We have made several analyses from different crystals and Cu was only present on surface. We have also analyzed some crystals with EPMA and results are totally consistent with values acquired by FE-SEM-EDS.
On Ulldemolins cechite crystals it is usual to find other mineral species on the surface, like mottramite or, more rarely, calderonite.
We have also a LIBS spectra made by Adolf Cortel and different RAMAN spectra those show similar structures like pyrobelonite-descloizite-mottramite. That's why only RAMAN is incomplete to confirm species.
We are working on other analyses and studies and preparing an article (as indicated in mindat Ulldemolins page) for the next magazine of Grup Mineralògic Català. It would have been great if you had contacted us in order to discuss the results. But never is too late...
Back to top
Reply to topic Reply with quote
Like
5
   
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 2006-2017


Powered by FMF