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
18 Mar-08:12:52 Green seam. Looks like it in a state of decay. (Ning)
18 Mar-06:47:13 Mineralogy & museums 10 - cardiff - 12th-13th august 2024 (Roy Starkey)
18 Mar-02:50:32 Re: collection from dany mabillard (Dany Mabillard)
17 Mar-01:57:58 Re: collection of volkmar stingl (Volkmar Stingl)
15 Mar-14:27:47 Re: collection of philippe durand (Philippe Durand)
15 Mar-13:49:04 Re: collection of firmo espinar (Firmo Espinar)
15 Mar-09:18:42 Re: collection of michael shaw (Michael Shaw)
15 Mar-03:45:43 The mizunaka collection - rhodochrosite (Am Mizunaka)
14 Mar-21:29:31 Re: monthly mineral chronicles, mineral guides and more... (Crocoite)
14 Mar-14:47:27 Re: collection of philippe durand (Jordi Fabre)
14 Mar-13:56:01 Re: collection of philippe durand (Philippe Durand)
14 Mar-11:24:43 Re: collection of philippe durand (Jordi Fabre)
14 Mar-08:55:22 Re: collection of michael shaw (Michael Shaw)
14 Mar-08:44:47 Re: the mim museum in beirut, lebanon (Mim Museum)
14 Mar-07:24:12 Re: collection of volkmar stingl (Volkmar Stingl)
14 Mar-02:30:15 The mizunaka collection - quartz (Am Mizunaka)
14 Mar-02:20:37 Re: collection of volkmar stingl (Tobi)
13 Mar-23:40:08 Re: collection of volkmar stingl (Volkmar Stingl)
13 Mar-14:22:58 Re: don lum collection (Don Lum)
13 Mar-14:02:43 Re: collection of philippe durand (Philippe Durand)
13 Mar-00:57:48 The mizunaka collection - quartz (Am Mizunaka)
12 Mar-07:36:06 Re: can you recommend a lab to analyse specimens (Luiz Oliveira)
11 Mar-16:19:18 Re: collection of philippe durand (Riccardo Modanesi)
11 Mar-15:18:26 Re: collection of philippe durand (Philippe Durand)
11 Mar-15:13:07 Re: collection of philippe durand (Philippe Durand)

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
111632


The time now is Mar 19, 2024 06:16

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.
Help with mineral identification in thin section from Khibiny, Kola peninsula
  
  Index -> Minerals and Mineralogy
Like
2


View previous topic :: View next topic  
Author Message

Daniel Garcia




Joined: 02 May 2022
Posts: 16
Location: Narbonne

View user's profile

Send private message

PostPosted: May 14, 2022 10:40    Post subject: Help with mineral identification in thin section from Khibiny, Kola peninsula  

Hi

I'm trying to identify some rare minerals in thin sections from urtites collected in Khibiny in 2005. Maybe somebody is familiar with these minerals.

In these pictures, the clear groundmass is nepheline, and the green laths are aegirine.
The poikilitic mineral in the center of the second picture is eudialyte, and the orange laths are (presumably) astrophyllite.

My question is about the (almost isotropic) black mineral with almost the same shape as astrophyllite and sometimes contains nepheline inclusions. Could this be aenigmatite ?

Thanks in advance



KY03C_2LN.jpg
 Mineral: Eudialyte
 Dimensions: 3 mm
 Description:
thin sections in non polarised light
 Viewed:  4513 Time(s)

KY03C_2LN.jpg


Back to top
Reply to topic Reply with quote
Like
   

Pete Modreski
Site Admin



Joined: 30 Jul 2007
Posts: 709
Location: Denver, Colorado


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: May 14, 2022 12:47    Post subject: Re: Help with mineral identification in thin section from Khibiny, Kola peninsula  

Hi Daniel, seems that only one picture made it attached?

I've been there and like these kinds of rocks, but probably don't know enough to offer a sure guess or confirmation tho!

Pete
Back to top
Reply to topic Reply with quote
Like
   

Daniel Garcia




Joined: 02 May 2022
Posts: 16
Location: Narbonne

View user's profile

Send private message

PostPosted: May 14, 2022 15:59    Post subject: Re: Help with mineral identification in thin section from Khibiny, Kola peninsula  

Hi Pete

I'm not familiar with the forum desk, hence my first picture was discarded. Second try.

Like previously, the green laths are aegirine, the clear groundmass is nepheline and the orange laths should be astrophyllite.
No eudialyte in this picture, but the (unknown) black laths again, intergrown with aegirine.



KY03C_1LN.jpg
 Mineral: Aegirine
 Locality:
Khibiny Massif, Kola Peninsula, Murmanskaja Oblast, Northern Region, Russia
 Dimensions: 3 mm
 Description:
thin section
 Viewed:  4458 Time(s)

KY03C_1LN.jpg


Back to top
Reply to topic Reply with quote
Like
1
   

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: May 16, 2022 01:49    Post subject: Re: Help with mineral identification in thin section from Khibiny, Kola peninsula  

Daniel - According to MacKenzie & Guilford (1980) 'Atlas of rock-forming minerals in thin section', aenigmatite may appear opaque but the deep brown colour is pleochroic,. So perhaps you can increase the light to try to see the pleochroism, by rotating the polarizer in PPL.
Back to top
Reply to topic Reply with quote
Like
1
   

Daniel Garcia




Joined: 02 May 2022
Posts: 16
Location: Narbonne

View user's profile

Send private message

PostPosted: May 16, 2022 03:20    Post subject: Re: Help with mineral identification in thin section from Khibiny, Kola peninsula  

Thanks Duncan, good idea

In my textbooks too, aenigmatite is said to have a strong pleochroism, but often obscured by the color. It is classified as "nearly opaque" by W.E. Troger.
Indeed, with a higher magnification, a higher light power, and where the mineral is thinner than the normal 35 microns in contact with inclusions, I do see the brownish coulour and the pleochroism.
Is that conclusive ?

Otherwise, I don't feel very comfortable with the shape. The crystals look like slightly curved discs, with very acute terminations like here, In the textbook, they say "columnar" instead.



20220516-100409-357.jpg
 Mineral: Aenigmatite?
 Description:
 Viewed:  4356 Time(s)

20220516-100409-357.jpg


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: May 16, 2022 05:41    Post subject: Re: Help with mineral identification in thin section from Khibiny, Kola peninsula  

I don't know if the colour and pleochroism are diagnostic, but your images certainly "look" like those in MacKenzie & Guilford, including one with an acute termination. What else might the dark laths be? Can you eliminate any likely alternatives? (Remember, you are looking at 2D sections of 3D crystals, so they could be "columnar".)
Back to top
Reply to topic Reply with quote
Like
   

Daniel Garcia




Joined: 02 May 2022
Posts: 16
Location: Narbonne

View user's profile

Send private message

PostPosted: May 16, 2022 08:20    Post subject: Re: Help with mineral identification in thin section from Khibiny, Kola peninsula  

Duncan Miller wrote:
I don't know if the colour and pleochroism are diagnostic, but your images certainly "look" like those in MacKenzie & Guilford, including one with an acute termination. What else might the dark laths be? Can you eliminate any likely alternatives? (Remember, you are looking at 2D sections of 3D crystals, so they could be "columnar".)


Thanks, but I don't have access to this treatise.
I agree that a section is not a 3D view, anyway.
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 2006-2024


Powered by FMF