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
01 Apr-19:33:25 Re: a mineralogical trip through the states of usa - oklahoma (Michael Shaw)
01 Apr-16:18:18 Re: a mineralogical trip through the states of usa - oklahoma (Michael Shaw)
01 Apr-15:52:36 Stannite with zinkenite from bolivia / mvm (minerals - virtual museum) collection (Jordi Fabre)
01 Apr-15:13:19 Re: carlos pareja photo collection (Carlos Pareja)
01 Apr-10:02:31 Re: collection of enrique llorens (Enrique Llorens)
01 Apr-09:46:41 Re: help , please, with locality (Kevin Schofield)
01 Apr-08:01:21 Re: hemimorphite (Forrestblyth)
01 Apr-07:37:09 Re: help , please, with locality (Tobi)
01 Apr-06:16:00 Re: hemimorphite (Forrestblyth)
01 Apr-06:10:08 Re: hemimorphite (Forrestblyth)
01 Apr-05:44:55 Re: hemimorphite (Forrestblyth)
01 Apr-05:40:30 Re: hemimorphite (Forrestblyth)
01 Apr-05:35:14 Hemimorphite (Forrestblyth)
01 Apr-04:58:36 The forrestblyth collection (Forrestblyth)
01 Apr-01:20:26 The mizunaka collection - gypsum (Am Mizunaka)
31 Mar-23:20:16 Re: presentation of new members - travis from franklin, new jersey (Don Lum)
31 Mar-18:41:27 Re: presentation of new members - travis from franklin, new jersey (Michael Shaw)
31 Mar-17:40:57 Presentation of new members - travis from franklin, new jersey (Franklinite1988)
31 Mar-14:00:32 Spinel on calcite from pein-pyit / mvm (minerals - virtual museum) collection (Jordi Fabre)
31 Mar-12:26:22 Help , please, with locality (Danovskim)
31 Mar-10:53:36 Re: collection of tobi (Tobi)
31 Mar-08:54:42 Re: collection of michael shaw (Michael Shaw)
30 Mar-23:41:39 Re: collection of volkmar stingl (Volkmar Stingl)
30 Mar-18:30:21 The mizunaka collection - fluorite (Am Mizunaka)
30 Mar-14:54:50 Re: collection of matteo chinellato (Danovskim)

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
119838


The time now is Apr 02, 2025 03:01

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.
Fluorite crystallography?
  Goto page Previous  1, 2
  Index -> Minerals and Mineralogy
Like
18


View previous topic :: View next topic  
Author Message

Pete Richards
Site Admin



Joined: 29 Dec 2008
Posts: 841
Location: Northeast Ohio


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Nov 28, 2023 08:35    Post subject: Re: Fluorite crystallography?  

Carles Millan wrote:
So it is {100}{110}.

Yes, it is {100}{110}. I checked my small collection of Naica fluorites last night, and mine also have this habit.

An interesting extra is that some of them have an overall octahedral shape, like ones that Peter Megaw illustrated. In spite of the overall shape, the faces on the specimen are all cube or dodecahedral faces. It seems quite likely that there was a first generation that was octahedral, and the second generation of cube and dodecahedron overgrew it. I'll add a photo if I can get a decent one....

_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy
Back to top
Reply to topic Reply with quote
Like
   

Tobi
Site Admin



Joined: 07 Apr 2009
Posts: 4228
Location: Germany


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Nov 28, 2023 10:00    Post subject: Re: Fluorite crystallography?  

Tobi wrote:
Peter Megaw wrote:
Tobi...could I get high-rez versions of these images with permission to publish? I am working on an article on Naica and these are worth considering for inclusion.
I'll let you know if a larger (and better) version is possible ;-)
Hi Peter, I just received an answer from Rudi Watzl's assistant Konrad, he sent me the largest version of the file that they have. Resolution is the same but the file size is much larger, I hope this image that I attached to this post is good enough for you?

Concerning the credits he wrote:
"Natürlich könnt ihr das Foto gerne auch veröffentlichen. Bitte bei den Credits „Foto: Saphira Minerals“ schreiben." ("Of course you are welcome to publish the photo. Please write “Photo: Saphira Minerals” in the credits.")

So please feel free to use it :-)

Regards
Tobi



FA254-aCMYK.jpg
 Mineral: Fluorite, Sphalerite
 Locality:
Naica Mine, Naica, Municipio Saucillo, Chihuahua, Mexico
 Dimensions: Specimen height 8 cm
 Description:
Photo: Saphira Minerals
 Viewed:  75501 Time(s)

FA254-aCMYK.jpg


Back to top
Reply to topic Reply with quote
Like
1
   

Jesse Fisher




Joined: 18 Mar 2009
Posts: 638
Location: San Francisco


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Nov 28, 2023 11:08    Post subject: Re: Fluorite crystallography?  

Another Naica fluorite, which according to Pete's analysis would be cube-dodechahedral habit. From the find circa 2005.


F323-2050r.JPG
 Mineral: Fluorite on Sphalerite
 Locality:
Naica Mine, Naica, Municipio Saucillo, Chihuahua, Mexico
 Dimensions: 14x10x6 cm
 Description:
cube-dodecahedral habit, with inclusions of what appears to be pyrite.
 Viewed:  75433 Time(s)

F323-2050r.JPG


Back to top
Reply to topic Reply with quote
Like
2
   

Bob Morgan




Joined: 18 Jan 2018
Posts: 247
Location: Savannah, Georgia


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Nov 28, 2023 11:45    Post subject: Re: Fluorite crystallography?  

Pete,
Some of us call these 'Mayan Temple" habit fluorites. Yes, these are the result of smaller overgrowths on octahedral crystals. I have a specimen from Naica that has an octahedral phantom sprinkled with small galena crystals, that can be seen through clear cube faces at the terminations of the underlying octahedron. This particular specimen has overgrowths that are cubes with small dodecahedral faces and larger trapezohedral faces and the occasional small octahedral face.
The original octahedral stage is an indication of a higher temperature of formation, which is supported by the octahedral habit of the small galena crystals. Subsequent overgrowths then were lower temperature aligned deposits more characteristic of cube shapes.
'Myan Temple' habit fluorites come from other places. I've seen them from Dalnegorsk, China and even places in the US that I can't recall.
Larger overgrowths tend to be on the octahedral terminations with smaller ones down the octahedral edges and even smaller ones stepping all over underlying octahedral faces.
Back to top
Reply to topic Reply with quote
Like
   

Pete Richards
Site Admin



Joined: 29 Dec 2008
Posts: 841
Location: Northeast Ohio


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Nov 28, 2023 13:40    Post subject: Re: Fluorite crystallography?  

Bob Morgan wrote:
(snip)
Larger overgrowths tend to be on the octahedral terminations with smaller ones down the octahedral edges and even smaller ones stepping all over underlying octahedral faces.


Bob's comments about overgrowth patterns are supported by the photos below of one of my Naica specimens. Peter Megaw's photos earlier also show the general pattern of overgrowth on an earlier octahedron - particularly the second one in which the overgrowth is only minimal.

The slower and somewhat chaotic overgrowth in the middles of the original octahedral faces leaves them depressed in comparison to the corners and edges adorned by the cube and dodecahedral faces.



IMG_8039.JPG
 Mineral: Fluorite
 Locality:
Naica, Municipio Saucillo, Chihuahua, Mexico
 Dimensions: 2 cm
 Description:
View showing cube and dodecahedal overgrowths on a corner and edges of a former octahedral crystal. Natural light.
 Viewed:  75344 Time(s)

IMG_8039.JPG



IMG_8007.JPG
 Description:
 Viewed:  75533 Time(s)

IMG_8007.JPG



IMG_7978.JPG
 Mineral: Fluorite
 Locality:
Naica, Municipio Saucillo, Chihuahua, Mexico
 Description:
Top view with cube face highlighted. Artificial light.
 Viewed:  75372 Time(s)

IMG_7978.JPG



_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy
Back to top
Reply to topic Reply with quote
Like
   

Bob Morgan




Joined: 18 Jan 2018
Posts: 247
Location: Savannah, Georgia


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 04, 2023 12:19    Post subject: Re: Fluorite crystallography?  

The picture you feature under your name is cube-octahedral.
Back to top
Reply to topic Reply with quote
Like
   

Bob Morgan




Joined: 18 Jan 2018
Posts: 247
Location: Savannah, Georgia


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 04, 2023 12:23    Post subject: Re: Fluorite crystallography?  

The picture I referenced is under Carles Millan's name.
Back to top
Reply to topic Reply with quote
Like
   

Johan Kjellman




Joined: 10 Jan 2014
Posts: 19
Location: Uppsala

View user's profile

Send private message

PostPosted: Dec 12, 2023 17:58    Post subject: Re: Fluorite crystallography?  

Jesse Fisher wrote:
Another Naica fluorite, which according to Pete's analysis would be cube-dodechahedral habit. From the find circa 2005.


I 100 % agree with Pete's analysis of how to differentiate between the two combinations.
But in the case of this (Jesse's) fluorite it appears to me to be a cube-octahedron.

cheers
Back to top
Reply to topic Reply with quote
Like
   

Bob Morgan




Joined: 18 Jan 2018
Posts: 247
Location: Savannah, Georgia


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 12, 2023 18:03    Post subject: Re: Fluorite crystallography?  

Yes.
Back to top
Reply to topic Reply with quote
Like
   

Pete Richards
Site Admin



Joined: 29 Dec 2008
Posts: 841
Location: Northeast Ohio


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 12, 2023 20:52    Post subject: Re: Fluorite crystallography?  

I am not sure how to interpret Jesse's fluorite. I cannot see any view that is unambiguous. It appears that the cube faces are clear, maybe slightly pebbled, and that the other faces are frosted.

In the bottom-most fluorite in his specimen, the lower left corner of the forward-facing cube face points to the edge between a pair of the other faces, beyond which is a face that is just barely visible because it is nearly perpendicular to the view. This face holds the answer. If it is a cube face, then the habit is cube-octahedral; if it is one of the other, frosted faces, the habit is cube-dodecahedral.

The crystal on the upper left also helps a little. It has a cube face oriented forward and slightly down. Above and to the right of this face are two of the other faces. To the top-right of these is another face, sloping backwards. It is hard to see clearly, but it appears to me to be frosted. If so, this crystal also indicates a cube-dodecahedral habit; if instead this is a cube face, then the habit is cube-octahedral.

In my view, and with considerable uncertainty, the habit of this one is, like the other examples, cube-dodecahedral - (100)(110). Perhaps Jesse will look at his specimen from all angles and let us know!

_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy
Back to top
Reply to topic Reply with quote
Like
   

Bob Morgan




Joined: 18 Jan 2018
Posts: 247
Location: Savannah, Georgia


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 12, 2023 22:29    Post subject: Re: Fluorite crystallography?  

Pete,
Points well stated.
I looked at photos in Mindat of fluorite on sphalerite. Nearly all were cube- dodecahedral that could be discerned clearly.
Back to top
Reply to topic Reply with quote
Like
   

Johan Kjellman




Joined: 10 Jan 2014
Posts: 19
Location: Uppsala

View user's profile

Send private message

PostPosted: Dec 13, 2023 02:57    Post subject: Re: Fluorite crystallography?  

I agree again - and withdraw my claim.
And Pete, you point directly at what I now think so many of us, although experienced, keep on misinterpreting these combos. We are all fast and confident in identifying the first prominent cube face. Then a "second face" a bit too quickly identified as a cube and, voila, you have a cube-octahedron.
Maybe we all should slow down and look for a third alternative cube face. I (think I) see them in both crystals you described on Jesse's specimen.The thing is, and this may be part of the problem, these cube faces seem relatively smaller than the obvious large one.

cheers
Back to top
Reply to topic Reply with quote
Like
   

Pete Richards
Site Admin



Joined: 29 Dec 2008
Posts: 841
Location: Northeast Ohio


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 13, 2023 09:42    Post subject: Re: Fluorite crystallography?  

Johan Kjellman wrote:
(snip)
The thing is, and this may be part of the problem, these cube faces seem relatively smaller than the obvious large one.


Yes, definitely. These crystals show substantial deviations from ideally developed morphology, where all faces of a given form would have the same size and shape. Several of the dodecahedral faces appear to have nice three-fold symmetry, which is a false impression, but possible since these faces have six edges. With a little distortion, they can present as alternating long and short edges, and voila, pseudo-three-fold symmetry. The angles between the edges would be wrong for three-fold symmetry, but this is very hard to judge when a face is tilted.

_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy
Back to top
Reply to topic Reply with quote
Like
   

Johan Kjellman




Joined: 10 Jan 2014
Posts: 19
Location: Uppsala

View user's profile

Send private message

PostPosted: Oct 01, 2024 05:15    Post subject: Re: Fluorite crystallography?  

I came back to this thread, having forgotten and identified the first image first as a cube-octahedron, but then, after counting the exposed faces of the most obvious crystal (I could see 8) I came to the conclusion that it must be a cube-dodecahedron. Because you can never see more faces than half of what the crystal have from one side. I am quite confident that this applies even to distorted crystals, even stepped crystals if you count repeatedly oriented faces as 1.

So, I propose the following "half-face" method, not bulletproof, but works in many instances.
cube + octahedron = 6 + 8 faces = 14, one should not be able to see more than 7 faces
cube + dodecahedron = 6 + 12 faces = 18, i.e. not more than 9

I attach a hastily prepared sketch. The top two crystals are different but oriented in a way that minimize the number of the exposed faces. This illustrates the general problem.
On the bottom row I have tilted both crystals, and you can now count the exposed faces.



cubenigmeder.JPG
 Description:
 Viewed:  3442 Time(s)

cubenigmeder.JPG


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 2 of 2
  Goto page Previous  1, 2  

 
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 2006-2025


Powered by FMF