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Weird face in quartz
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Reef




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PostPosted: Nov 15, 2017 11:10    Post subject: Re: Weird face in quartz  

Hello, Pierre! On your photo, a parallel splice, at least 3 crystals. You see a rhombohedron of the third crystal. Such composite crystals an everyday occurrence.
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Pierre Joubert




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PostPosted: Nov 15, 2017 12:55    Post subject: Re: Weird face in quartz  

Reef wrote:
Hello, Pierre! On your photo, a parallel splice, at least 3 crystals. You see a rhombohedron of the third crystal. Such composite crystals an everyday occurrence.


Do you mind showing me something similar?

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PostPosted: Aug 09, 2018 13:52    Post subject: Re: Weird face in quartz  

Here is yet another unusual specimen that I found a few weeks ago. One side has a curved face all the way from the bottom to the termination point. I have never seen anything like it. I would appreciate it if anyone can shed some light on this mysterious occurrence.


P1420728.JPG
 Mineral: Quartz (variety smoky)
 Locality:
Villiersdorp, Theewaterskloof, Overberg, Western Cape, South Africa
 Dimensions: 88 x 40 x 29 mm
 Description:
 Viewed:  3970 Time(s)

P1420728.JPG



P1420734.JPG
 Mineral: Quartz (variety smoky)
 Locality:
Villiersdorp, Theewaterskloof, Overberg, Western Cape, South Africa
 Dimensions: 88 x 40 x 29 mm
 Description:
 Viewed:  3969 Time(s)

P1420734.JPG



P1420736.JPG
 Mineral: Quartz (variety smoky)
 Locality:
Villiersdorp, Theewaterskloof, Overberg, Western Cape, South Africa
 Dimensions: 88 x 40 x 29 mm
 Description:
 Viewed:  3958 Time(s)

P1420736.JPG



P1420740.JPG
 Mineral: Quartz (variety smoky)
 Locality:
Villiersdorp, Theewaterskloof, Overberg, Western Cape, South Africa
 Dimensions: 88 x 40 x 29 mm
 Description:
 Viewed:  3967 Time(s)

P1420740.JPG



P1420741.JPG
 Mineral: Quartz (variety smoky)
 Locality:
Villiersdorp, Theewaterskloof, Overberg, Western Cape, South Africa
 Dimensions: 88 x 40 x 29 mm
 Description:
 Viewed:  3969 Time(s)

P1420741.JPG



P1420746.JPG
 Mineral: Quartz (variety smoky)
 Locality:
Villiersdorp, Theewaterskloof, Overberg, Western Cape, South Africa
 Dimensions: 88 x 40 x 29 mm
 Description:
 Viewed:  3978 Time(s)

P1420746.JPG



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Bob Morgan




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PostPosted: Aug 09, 2018 21:17    Post subject: Re: Weird face in quartz  

Amen to your question. I have a similarly bent quartz that came with the only identifier of locality as Madagascar.
It isn't like a gwindel - bent in different direction. The surface is smooth and almost waxy.
I look forward to the explanations!
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PostPosted: Aug 10, 2018 02:37    Post subject: Re: Weird face in quartz  

Bob Morgan wrote:
Amen to your question. I have a similarly bent quartz that came with the only identifier of locality as Madagascar.
It isn't like a gwindle - bent in different direction. The surface is smooth and almost waxy.
I look forward to the explanations!


Hi Bob. This crystal is not bent at all. The 'curve' is slightly twisted and runs the length of the crystal. Looking forward to seeing your specimen.

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PostPosted: Aug 10, 2018 14:53    Post subject: Re: Weird face in quartz  

I should have said the face is curved. My specimen isn't bent either, another distinction from Gwindels.
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PostPosted: Aug 13, 2018 13:34    Post subject: Re: Weird face in quartz  

Pierre Joubert wrote:
Here is yet another unusual specimen that I found a few weeks ago. One side has a curved face all the way from the bottom to the termination point. I have never seen anything like it. I would appreciate it if anyone can shed some light on this mysterious occurrence.


I observe that the crystal appears to be fractured in several places. I wonder if the curved surface could be a large conchoidal fracture that removed that portion of the crystal. Perhaps there was a little secondary growth or etching, or perhaps not. I know this is not a very exciting proposal, but quartz IS known for its conchoidal fracture.

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PostPosted: Aug 13, 2018 14:38    Post subject: Re: Weird face in quartz  

Pete Richards wrote:
Pierre Joubert wrote:
Here is yet another unusual specimen that I found a few weeks ago. One side has a curved face all the way from the bottom to the termination point. I have never seen anything like it. I would appreciate it if anyone can shed some light on this mysterious occurrence.


I observe that the crystal appears to be fractured in several places. I wonder if the curved surface could be a large conchoidal fracture that removed that portion of the crystal. Perhaps there was a little secondary growth or etching, or perhaps not. I know this is not a very exciting proposal, but quartz IS known for its conchoidal fracture.


Hi Pete. Thank you for your input. The 'curve' is much too consistent for a fracture (I suppose it is not impossible). There is a black unknown mineral that has formed with the crystals in this pocket. The black mineral is included in many of the crystals and in many cases, weathered away leaving deep 'channels' in the crystals. I will attempt to show photos of this strange occurrence soon. This is indeed a strange find. Perhaps the black mineral somehow contributed to the formation of this strange curve.

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PostPosted: Aug 14, 2018 15:05    Post subject: Re: Weird face in quartz  

Here're pics of my curve faced quartz, Every terminal face is curved though two are radically so. There are some curved patches of prism faces also. On one corner where 's' and 'x' faces might appear there is a appropriately shaped structure that stands out as if less effected by etching that might cause the other curved faces. The one pyramidal face with triangular hillocks has slightly different orientations - the top being different from the bottom pyramid faces. This also seems to show signs of c-axis twinning to help account for this.


P8140001 (3).JPG
 Locality:
Madagascar
 Description:
 Viewed:  3729 Time(s)

P8140001 (3).JPG



P8140004 (2).JPG
 Mineral: q
 Locality:
Madagascar
 Description:
 Viewed:  3744 Time(s)

P8140004 (2).JPG



P8140016 (3).JPG
 Mineral: Quartz
 Locality:
Madagascar
 Dimensions: 9.2cm x10.8cm
 Description:
 Viewed:  3739 Time(s)

P8140016 (3).JPG



P8140009 (3).JPG
 Description:
 Viewed:  3737 Time(s)

P8140009 (3).JPG


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PostPosted: Aug 15, 2018 05:51    Post subject: Re: Weird face in quartz  

Hi Bob. Very interesting! P8140016 (3).JPG
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PostPosted: Oct 01, 2018 23:09    Post subject: Re: Weird face in quartz  

In the photo in the upper left, the long thin reflection appears to be the 's' face. If so, on the other side of the adjoining indefinite (striated) area in between is probably a (212) sliver. As to the odd face perhaps it is a 'u' face (311). Unfortunately I can't do a drawing to check this out. My computer with my old Shape program gave out tonight.

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PostPosted: Oct 01, 2018 23:14    Post subject: Re: Weird face in quartz  

This latest submission refers back to Josele's crystal https://www.mineral-forum.com/message-board/download.php?id=74577 in https://www.mineral-forum.com/message-board/viewtopic.php?p=54392#54392 that started this discussion in November of 2016
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PostPosted: Feb 06, 2020 11:36    Post subject: Re: Weird face in quartz  

Reef wrote:
Sometimes a rhombohedron (012) is replaced by a ditrigonal scalenohedron. Together with {012}, on the vertex there are occasional faces from (103) to (1.0.11), down to the pinacoid (001).

I apologize for the mistake I made. Correction: Sometimes the rhombohedron (012) is replaced by the left and right trigonal trapezohedron.



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15 (1).jpg



15 (2).jpg
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15 (2).jpg


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