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Inclusions of spiral or helical growth and screw dislocations - (0)
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Elise




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PostPosted: Mar 31, 2013 08:57    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Hi Duncan!
Great fun that you picked this thread back up! The Rochester Mineralogical Symposium is coming up very soon - helical fans John White and John Rakovan will both be there and Bill will be nearby -- it would be a wonderful time to sit and brainstorm this fascinating formation. There is still time to book a flight ;-) or we can put you on SKYPE! Speaking of which, getting on a plane now headed for the Sinkankas Symposium...We'll have fun discussing this thread on the trip and we will get back with any " high altitude, bright ideas", if any occur!
Cheers!
Elise
xenolithos wrote:
I think that these helical growth/etch features, and the macroscopic growth hillocks seen on many crystal faces (see Rakovan 2004), really should not be called 'screw dislocations' even if one or more screw dislocations originally played some part in their formation. Helical dislocations are not pure screw dislocations, and most dislocations have a mixed edge/screw characteristic, occur in high density and on a microscopic scale.

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PostPosted: Mar 20, 2014 21:50    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Hi Everyone,

Elise brought this fascinating thread to my attention after I posted this photo of a screw-dislocated natrolite on Facebook. I must admit, most of this discussion is way over my head, but I'm happy to be able to contribute, and looking forward to learning more about it!

BTW, I showed this to John Rakovan in Tucson when I got it, and he's interested in studying it, so I'll post any new information that comes out of it.

Michael



20140316_1757.jpg
 Description:
natrolite
Mount Saint Hilaire, Quebec, Canada
2.7cm high
 Viewed:  14844 Time(s)

20140316_1757.jpg


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Duncan Miller




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PostPosted: Mar 21, 2014 00:36    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

When I listed the minerals in which these helical growth features\screw dislocations (?) had been observed, I forgot to mention natrolite. Thank you for reminding me. I have seen several in natrolite specimens from a quarry near Hardap Dam, Mariental, Namibia.
Duncan

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marco campos-venuti




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PostPosted: Jun 10, 2014 06:29    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Another example in tourmaline from Madagascar


IMG_2177 (Medium).JPG
 Description:
Tourmaline
Ibity, Madagascar
2 cm
 Viewed:  14444 Time(s)

IMG_2177 (Medium).JPG


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marco campos-venuti




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PostPosted: Jul 16, 2014 05:09    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

I would like to restart this interesting topic.
We use the term spiral dislocation because we have in mind the screw dislocation studied in crystal growth. We realize, speaking in this thread, that the scale is so different that we are probably in front of a different thing. We can then call it just fractures.
First we better we try to analyze these spiral structures. We have 2 different structures presented in the pictures in this thread.
1- a spiral fracture aligned along the long axis of the crystal (as in the Aquamarine of François Lietard )
2- many “en echelon” fractures (as in the John Koivula photo)
I found spirals in chalcedony and in opals. I have interpreted them as conchoidal fractures formed by contraction stress during loss of water in the free surface of small opal ponds. (see picture of chalcedony)
I reproduced this at home using egg white (see picture) that is a similar gel material.
What is the relation of these spirals in amorphous material with spirals in crystals, I don't know. Maybe there is no relation.
But the second style of fractures looks to me like a more clear stress pattern, due to geological deformation or simply to the contact of two different materials. As is the case of this picture of a quartz with lithyophilite inclusions. I'm not sure about the inclusions, they could be a mica. In this case the stress is confined at the boundary between quartz and the edge of the lithyophilite crystal. It is not rare that the inclusion crystals induce fractures in the included crystal. In this case the fractures are “en echelon”, maybe because the inclusion is flat.
I can't bring any conclusions, but I hope someone help me to reopen this topic,
marco



IMG_1911 (Medium).JPG
 Description:
quartz with lithyophilite inclusion
Brazil
26.2 cts
 Viewed:  14129 Time(s)

IMG_1911 (Medium).JPG



IMG_1909 (Medium).JPG
 Description:
quartz with lithyophilite inclusion
Brazil
26.2 cts
 Viewed:  14147 Time(s)

IMG_1909 (Medium).JPG



buona 2 (Small).JPG
 Description:
Dryed eggs white
at home
field is 5 cm
The pattern is the same as in the chalcedony
 Viewed:  14134 Time(s)

buona 2 (Small).JPG



2.JPG
 Description:
Chalcedony
Milos, Greece
field is 4 cm
The specimen shows many spirals on the same horizontal surface
 Viewed:  14134 Time(s)

2.JPG


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Elise




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PostPosted: Nov 21, 2014 12:56    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

marco campos-venuti wrote:
I can't bring any conclusions, but I hope someone help me to reopen this topic


Hi Marco!
thank you so much for jump-starting this thread again,even if I am late finding your additions! The chalcedony spirals are fascinating!

Our discussion crosses many borders and has been going on for years now. We are all looking forward to John White & John Rakovan's published paper to shed some more light on it (presented at the Rochester Mineralogical Symposium a couple years ago).

I am lucky to have a wonderful specimen faceted by Duncan from the same beryl crystal as his own, pictured further back in the thread. I haven't taken a nice picture of it yet, but here it is anyway (scale from the folks holding it). It has been the focus of much discussion off-forum and a delight to have in my collection.

Best wishes,
Elise



20140320_berylWABeas1a.jpg
 Mineral: Beryl
 Description:
 Viewed:  13603 Time(s)

20140320_berylWABeas1a.jpg



Beryl_5514a96.jpg
 Mineral: Beryl
 Description:
 Viewed:  13599 Time(s)

Beryl_5514a96.jpg


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PostPosted: Nov 21, 2014 14:52    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

That is a really nice one Elise!
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marco campos-venuti




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PostPosted: Nov 21, 2014 15:18    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Wow Elise, that piece make me dream.
I remembered that I have an other spiral in a quartz, of a quite different kind, but of similarly obscure origin. It is a biterminated quartz crystal from the lodo quarry in Brazil that has a "lodo spiral" inside, visible from both sides.
A have an idea in mind, but I wait for your interpretation.



IMG_3896.JPG
 Mineral: Quartz
 Locality:
Brazil
 Dimensions: 65 mm
 Description:
Side A
 Viewed:  13568 Time(s)

IMG_3896.JPG



IMG_3897.JPG
 Mineral: Quartz
 Locality:
Brazil
 Dimensions: 65 mm
 Description:
Side B
 Viewed:  13554 Time(s)

IMG_3897.JPG



IMG_3898.JPG
 Mineral: Quartz
 Locality:
Brazil
 Dimensions: 65 mm
 Description:
 Viewed:  13568 Time(s)

IMG_3898.JPG


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Elise




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PostPosted: Nov 22, 2014 08:33    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Marco,

That quartz specimen is now second only to my other favorite on FMF, that of Vic Rzonca's find: http://www.mineral-forum.com/message-board/viewtopic.php?p=25510#25510

I have no idea what growth mechanism could cause such a structure to form and await your thoughts - what a special piece it is! Thank you so much for sharing this with us! I sent a link to Si & Ann Frazier, John Koivula, John White and other quartz enthusiasts friends, so they might enjoy the discussion as well.

Elise

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PostPosted: Dec 02, 2014 14:08    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

marco campos-venuti wrote:
I remembered that I have an other spiral in a quartz, of a quite different kind, but of similarly obscure origin. It is a biterminated quartz crystal from the lodo quarry in Brazil that has a "lodo spiral" inside, visible from both sides.

Hi Marco,

I shared a link to this specimen with my quartz-loving friends and I've discussed it with several mineralogists - the most common comment is "WOW!". Talking with John Koivula yesterday on the phone, we wondered together what the exact orientation of the inclusion is. In the top photo, it appears that the view is through a rhombohedral face, but maybe a little angle off of the c-axis. Is the inclusion spiral around the c-axis, oriented parallel to it, or is unrelated to it?

I also wondered what it would look like from the side, does it also spiral up with the growth of the crystal or is it in a flat plane? what does it look like in 3D? There appear to be mineral inclusions in the spiral or at its interface with the quartz - if there are, are they remains of another inclusion that formed the spiral or triggered it? Is the spiral itself quartz and is it a separate crystal from the host quartz?

Waiting to hear your thoughts if you'll share them with us - It is such an intriguing specimen!

Best wishes,
Elise

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PostPosted: Dec 11, 2014 16:19    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

The world of crystals is full of oddities, but the spiral is always an attraction for any people. The spiral is not on the C axis, but at 15-20 degrees. It is clearly not casual, because the spiral is composed of 2 branches with the same pattern. They make around 2 turns in a clockwise direction. The spiral grows with the growing crystal and reaches the surface in 2 points at 2 faces of the rhombohedron. It is clearly tridimensional. The spiral is made of small crystals, most of them look like white rhombohedral dolomite (or feldspar) mixed with some positive quartz crystals, and few yellow needles of a mineral different from rutile.
I will try to upload a video or to link to it if I learn how to do it.
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marco campos-venuti




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PostPosted: Dec 11, 2014 17:46    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

I uploaded a video of the crystal on youtube:
https://www.youtube.com/watch?v=ybcAAWND1D0
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PostPosted: Dec 11, 2014 19:54    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

this is so fantastic.
that would be amazing to try and photograph! (photomicrograph)

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Martin Rich




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PostPosted: Dec 11, 2014 23:24    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Sorry Marco for my silly statement, but is this a petrified hurricane? :)

Martin

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PostPosted: Feb 14, 2015 16:26    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

I was asked to post my aqua with an interesting spiral top and spiral inclusion. Not sure if they are associated or not, it seems to be more than coincidental but I honestly do not know. One thing I find strange about this piece is that half way down where the spiral jettisons out, you can see where it was trying to form the termination. So I don't know if this is an etching with a healing or if the spiral formation is a growth anomaly sprouting out the top in a 2nd generation of strange growth. Certainly an interesting piece that sparks a lot of interesting thought. I would love to hear from those that know more about how this might have been formed. Or even wild proposals of how this might happen. Anything in the interest of learning about this strange one is welcomed. I hope you enjoy it as much as I do :)
Regards,
Stretch



IMG_0946.JPG
 Mineral: Beryl variety Aquamarine
 Locality:
Shigar Valley, Skardu District, Baltistan, Gilgit-Baltistan (Northern Areas), Pakistan
 Dimensions: 2.4 x 1.3 x 1.0 cm
 Description:
My Aqua with a twist :)
 Viewed:  12103 Time(s)

IMG_0946.JPG



IMG_0945.JPG
 Mineral: Beryl variety Aquamarine
 Locality:
Shigar Valley, Skardu District, Baltistan, Gilgit-Baltistan (Northern Areas), Pakistan
 Dimensions: 2.4 x 1.3 x 1.0 cm
 Description:
showing a close up of the spiral top
 Viewed:  12119 Time(s)

IMG_0945.JPG



IMG_0947.JPG
 Mineral: Beryl variety Aquamarine
 Locality:
Shigar Valley, Skardu District, Baltistan, Gilgit-Baltistan (Northern Areas), Pakistan
 Dimensions: 2.4 x 1.3 x 1.0 cm
 Description:
showing a close up of the spiral inclusion
 Viewed:  12102 Time(s)

IMG_0947.JPG


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PostPosted: Feb 18, 2015 16:19    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Stretch - Thanks so much for adding these pictures of this extraordinary specimen to this thread (I had asked him to). I'm looking forward to any ideas members might have regarding what is happening in this specimen and how the formation at the top relates, if at all, to the inclusion. Are there any close-ups of the inclusion itself?

Best wishes,
Elise


Stretch wrote:
I was asked to post my aqua with an interesting spiral top and spiral inclusion. Not sure if they are associated or not, it seems to be more than coincidental but I honestly do not know. One thing I find strange about this piece is that half way down where the spiral jettisons out, you can see where it was trying to form the termination. So I don't know if this is an etching with a healing or if the spiral formation is a growth anomaly sprouting out the top in a 2nd generation of strange growth. Certainly an interesting piece that sparks a lot of interesting thought. I would love to hear from those that know more about how this might have been formed. Or even wild proposals of how this might happen. Anything in the interest of learning about this strange one is welcomed. I hope you enjoy it as much as I do :)
Regards,
Stretch

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PostPosted: Feb 19, 2015 07:22    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Stretch - That is really an astonishing beryl specimen. Would it be possible to post a video of it on a rotating turntable?
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PostPosted: Oct 13, 2015 10:53    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

I found an other strange spiral growth. This is an aragonite specimen from an old collection, labeled as coming from Stratoni, Chalkidiki, Greece.
No idea why it is spiral shaped,
marco



2766 (Medium).JPG
 Mineral: Aragonite
 Locality:
Stratoni operations, Cassandra Mines, Chalkidiki Prefecture, Macedonia Department, Greece
 Dimensions: 10 cm
 Description:
Aragonite spiral growth
 Viewed:  9724 Time(s)

2766 (Medium).JPG



IMG_1951.JPG
 Mineral: Aragonite
 Locality:
Stratoni operations, Cassandra Mines, Chalkidiki Prefecture, Macedonia Department, Greece
 Dimensions: 10 cm
 Description:
Aragonite spiral growth
 Viewed:  9740 Time(s)

IMG_1951.JPG


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PostPosted: Oct 13, 2015 15:24    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Hi Marco,

Fascinating aragonite. I wonder if the spiral growth could be the result of the aragonite replacing a gastropod.

Michael
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PostPosted: Oct 14, 2015 03:39    Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0)  

Hi Michael,
I was thinking the same. For the size and geometry it can be a Cerithioidea (Telescopium, family Potamididae). They are amphibious gastropod molluscs that live in brackish waters and are common in the fossil record. But its spiral is sinistral, that is quite unusual for this genera.
marco
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