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2014 - International year of crystallography: for example, pyrite.
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marco campos-venuti




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PostPosted: Jun 11, 2014 06:32    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Why not pyrite pseudo after pyrite?
Normal case of pyrite growing above pyrite is that the crystal continues to grow and nothing chance.
When we have epitaxial growths it is because for some reason, the nucleation increases and many small crystals grow oriented above the face of the previous pyrite, as is the case of these pictures (Las Palmas, Peru).
What is the reason for the disorder in the Racracancha crystals? Maybe the original crystal was in an unstable chemical condition and starts to be replaced by, for example, limonite. Before the process was completed, chemical conditions come back and pyrite is stable again, and starts to regrow replacing limonite. Result: pyrite pseudo after pyrite. (or pyrite pseudo after unknown mineral pseudo after pyrite). A little tricky, but realistic.



1983 (Medium).JPG
 Description:
Two generation of pyrite with epitaxial growths
Las Palmas, Perú
12 cm
 Viewed:  21323 Time(s)

1983 (Medium).JPG



1983b (Medium).JPG
 Description:
 Viewed:  21322 Time(s)

1983b (Medium).JPG


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Rei




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PostPosted: Jun 11, 2014 06:53    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Wow, that's... unusual.
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prcantos
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PostPosted: Sep 29, 2014 04:39    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

I would like to contribute to this interesting thread showing a pyrite crystal from Merelani Hills, Manyara, Tanzania. It is a complex crystal combining pyritohedron, octahedron, cube and trapezohedron (tetragon-trioctahedron) faces.


Sin título-0.jpg
 Mineral: Pyrite
 Locality:
Merelani Hills, Lelatema Mountains, Simanjiro District, Manyara Region, Tanzania
 Dimensions: 3 x 3 cm.
 Description:
A general view of this crystals. The global configuration approaches an icosahedron, an impossible form for crystals.
 Viewed:  20943 Time(s)

Sin título-0.jpg



Sin título-1.jpg
 Mineral: Pyrite
 Locality:
Merelani Hills, Lelatema Mountains, Simanjiro District, Manyara Region, Tanzania
 Dimensions: 2.5 x 2.5 cm.
 Description:
The faces: cube (c), octahedron (o), pyritohedron (p) and trapezohedron=tetragon-trioctahedron (t).
 Viewed:  21015 Time(s)

Sin título-1.jpg



esquema.jpg
 Description:
An ideal crystallographic scheme for this pyrite. Green cube {100}, blue octahedron {111}, orange pyritohedron {210} and grey trapezohedron {211}.
 Viewed:  20977 Time(s)

esquema.jpg



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Martin Rich




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PostPosted: Oct 03, 2014 14:47    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

I want to show an unusual habit of Pyrite. This crystal is extremely elongated. Length: 12 mm, diameter: 0.1 mm, this is a ratio of 1: 120!

Martin



Stengelpyrit_web.jpg
 Mineral: Pyrite, Calcite
 Locality:
Zöchling Quarry, Gaupmannsgraben, Ramsau bei Hainfeld, Mostviertel, Lower Austria, Lower Austria/Niederösterreich, Austria
 Dimensions: FOV about 20 mm
 Description:
Coll. Martin RichPhoto Harald Schillhammer, NHM Vienna
 Viewed:  20915 Time(s)

Stengelpyrit_web.jpg



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Josele




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PostPosted: Oct 03, 2014 18:27    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

What a weird pyrite! Sorry for my curiosity, don't want be prying but, how was it identified?
The only other photo of pyrite from the same quarry is quite different!

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Martin Rich




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PostPosted: Oct 04, 2014 14:54    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Hello Josele!

The crystal shown in the image is only visual identified. Ok, not very professional! Another, smaller xl was identified by XRD as pyrite and has a thin coating of Fe-oxides. Such elongated pyrite crystals are rare, but not uncommon in (organic material yielding) limestones like in the Zöchling quarry, Lower Austria. Millerite and silicate minerals as well, like Amphiboles, do not occur in this quarry.

Martin

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Jordi Fabre
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PostPosted: Oct 04, 2014 15:34    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Another example of elongated Pyrite (analyzed) from Minas da Panasqueira, Portugal


Pyriet with Fluorapatite and Siderite - Panasqueira Mines_Portugal.jpg
 Mineral: Pyrite with Fluorapatite and Siderite
 Locality:
Minas da Panasqueira, Aldeia de São Francisco de Assis, Covilhã, Castelo Branco, Cova da Beira, Centro, Portugal
 Dimensions: 6.5 × 4.6 × 3.2 cm
 Description:
Main crystal size: 2 × 1.3 cm
 Viewed:  20831 Time(s)

Pyriet with Fluorapatite and Siderite - Panasqueira Mines_Portugal.jpg


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Josele




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PostPosted: Oct 04, 2014 15:52    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

I wonder which forces act to develop so asymmetrical growth in an isometric mineral.
Definitely crystallography is as complex as it is fascinating.
Thanks for your kind explanations.

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Roger Warin




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PostPosted: Oct 04, 2014 16:25    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Hi,
Epitaxy on the same mineral is a parallel-axis growth. Contamination of the surface can prevent the second orderly growth.
Roger.
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prcantos
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PostPosted: Oct 05, 2014 17:51    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Diploid-shaped pyrite crystals from Duff Quarry. See https://www.mineral-forum.com/message-board/viewtopic.php?p=11208#11208 .


IMG_4448 copia.jpg
 Mineral: Pyrite
 Locality:
C. E. Duff & Son Quarry, Huntsville, Logan County, Ohio, USA
 Dimensions: FOV 4 cm.
 Description:
 Viewed:  20630 Time(s)

IMG_4448 copia.jpg



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prcantos
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PostPosted: Nov 11, 2014 08:36    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Another diploid-faced pyrite crystals. It comes from Respina Mine (León, Spain).

In this case we can recognize the diploid faces as half-pentagons on the pyritohedron. The height of this diploid is really low. Home-made measurement gives 175º for the dihedral angle between adjacent trapezoidal faces, which means a {0'098 2 1} ≈ {0'1 2 1} = {1 20 10} form: near a pyritohedron, but in fact a diploid {hkl} with h ≠ k ≠ l ≠ h.



IMG_4558 copia.jpg
 Mineral: Pyrite
 Locality:
Respina Mine, Fuentes de Respina, Puebla de Lillo, Comarca Valle de Boñar, León, Castile and León, Spain
 Dimensions: 5.5 x 4.5 cm.
 Description:
Pyrite in talc matrix. A false pyritohedron...
 Viewed:  20319 Time(s)

IMG_4558 copia.jpg



IMG_4560 copia.jpg
 Mineral: Pyrite
 Locality:
Respina Mine, Fuentes de Respina, Puebla de Lillo, Comarca Valle de Boñar, León, Castile and León, Spain
 Dimensions: 4 mm. the front edge
 Description:
... look at the line dividing the upper pentagon into two trapezoidal halves. They are in fact faces of the diploid. They appear in every 'pentagon' of this crystal, and can be detected mainly because of shining differences.
 Viewed:  20285 Time(s)

IMG_4560 copia.jpg



aproximacion.jpg
 Description:
Estimated ideal form for this specimen, a {0'098 2 1} ≈ {0'1 2 1} diploid, not a pyritohedron!
 Viewed:  20344 Time(s)

aproximacion.jpg



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marco campos-venuti




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PostPosted: Nov 11, 2014 10:10    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Josele wrote:
I wonder which forces act to develop so asymmetrical growth in an isometric mineral.
Definitely crystallography is as complex as it is fascinating.
Thanks for your kind explanations.


That's true Josele, look at this picture. They look as 3 monometric crystals, but only one is isometric. Crystallography is just a human approximation to nature.
-yellow crystal is a Garnet from Imilchil, Morocco
-brown crystal is a Dravite tourmaline crystal from Tomkap tourmaline mine, Yinnietharra, Western Australia
-green crystal is an Epidote crystal from Ras Koh Mts. near Kharan, Balochistan, Pakistan.



IMG_3842 (Medium).JPG
 Description:
-yellow crystal is a Garnet from Imilchil, Morocco
-brown crystal is a Dravite tourmaline crystal from Tomkap tourmaline mine, Yinnietharra, Western Australia
-green crystal is an Epidote crystal from Ras Koh Mts. near Kharan, Balochistan, Pakistan
 Viewed:  20293 Time(s)

IMG_3842 (Medium).JPG


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PostPosted: Nov 23, 2014 10:07    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

This pyrite crystal seen in Munich Show was for me the top of “my” International Year of Crystallography. It is a gorgeous crystal.
Roger.



125-Pyrite#1e_R.jpg
 Mineral: Pyrite
 Locality:
Huanzala Mine, Huallanca District, Dos de Mayo Province, Huánuco Department, Peru
 Dimensions: 7.5 cm
 Description:
 Viewed:  20072 Time(s)

125-Pyrite#1e_R.jpg


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prcantos
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PostPosted: Dec 16, 2014 18:10    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

Nanisivik Mine is well known for its pyrite crystals. They show faces according many different crystallographic forms.

In this specimen you can recognize the cube, the octahedron, the dodecahedron, the trapezohedron and the pyritohedron.



Sin título-4.jpg
 Mineral: Pyrite
 Locality:
Nanisivik Mine, Nanisivik, Baffin Island, Nunavut Territory, Canada
 Dimensions: 3.5 x 2.5 cm.
 Description:
 Viewed:  19606 Time(s)

Sin título-4.jpg



Sin título-3.jpg
 Mineral: Pyrite
 Locality:
Nanisivik Mine, Nanisivik, Baffin Island, Nunavut Territory, Canada
 Dimensions: 1 x 1 cm. crystal
 Description:
This crystal has cubic, octahedral and dodecahedral faces. The narrow face at the bottom right belongs to the trapezohedron.
 Viewed:  19611 Time(s)

Sin título-3.jpg



Sin título-2.jpg
 Mineral: Pyrite
 Locality:
Nanisivik Mine, Nanisivik, Baffin Island, Nunavut Territory, Canada
 Dimensions: FOV 2.5 cm.
 Description:
Another crystal with adds pyritohedral faces.
 Viewed:  19617 Time(s)

Sin título-2.jpg



Sin título-1.jpg
 Mineral: Pyrite
 Locality:
Nanisivik Mine, Nanisivik, Baffin Island, Nunavut Territory, Canada
 Dimensions: FOV 2.5 cm.
 Description:
Another complex crystal. Can you guess it?
 Viewed:  19619 Time(s)

Sin título-1.jpg



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Martin Rich




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PostPosted: Dec 30, 2014 15:35    Post subject: Re: 2014 - International year of crystallography: for example, pyrite.  

The international year of crystallography is still running!


Trepca; Pyrit 1.jpg
 Mineral: Pyrite, Calcite
 Locality:
Stan Trg (Stari Trg) Mine, Trepča Complex, Trepča Valley, Kosovska Mitrovica, Kosovska Mitrovica District, Kosovo
 Dimensions: 7.5 x 6.5 x 4 cm
 Description:
Complex aggregate of rounded pyrite crystals. Only {100} is clearly identifiable. New find from 2014.
 Viewed:  19477 Time(s)

Trepca; Pyrit 1.jpg



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