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Questionable gwindels

Posted by Harjo Neutkens  
Harjo Neutkens September 13, 2011 08:30PM
Following a facebook discussion about gwindels I thought to have at the gwindels on Mindat.
There are a few of which I'm not sure if they are actually gwindels.
Please feel free to correct me (especially Amir smiling smiley normal parallel growth not a combination of fadenquartz with a gwindel; fadenquartz only difficult to see, but I'm not sure there's a gwindel in the cluster not a combination of fadenquartz with a gwindel; fadenquartz only not sure, doesn't look twisted, so maybe normal parallel growth rehealed Quartz crystals "Gitterquarz" (oriented growth on Feldspar) very good gwindel disguise. But I think it's normal parallel growth (gwindel in pegmatite is unlikely) normal parallel growth I think normal parallel growth not sure.... not sure, but I think normal parallel growth normal parallel growth normal parallel growth very good disguise, but I think it's not a gwindel (unlikely in a pegmatite). tiny one, I looked at it for hours under the microscope and I'm quite sure it's a gwindel, but not 100% sure



Edited 1 time(s). Last edit at 09/13/2011 08:36PM by Harjo Neutkens.
Amir C. Akhavan September 14, 2011 01:02AM
1 & 2 likely not
3 faden (doesn't claim to be a gwindel)
4 bad shot (doesn't claim to be a gwindel)
5 just faden
6 no
7 likely not
8 gitterquartz, as written (doesn't claim to be a gwindel)
9 gwindel (I know because I saw a top view shot). In the discussion we heard that the poster was not sure about the exact locality (!?).
10 no
11 what is a "transitional gwindel"??? not sure
12 maybe, but not likely
13 unlikely (doesn't claim to be a gwindel)
14 unlikely, need a top view
15 unlikely
16 unlikely, need top view photo
17 we know that one winking smiley You should be able to tell, need top view photo

For 9, check description of locality

A lot of people are confused by the fact that quartz with macromosaic structure is often somewhat twisted around the c-axis and this is often reflected in the intergrowth of neighboring crystals.
Harjo Neutkens September 14, 2011 07:21AM
Thanks for 9 winking smiley then the locality maybe should be changed. Likely not from pegmatites around Shengus, but from the alpine-type environment in the nearby area.

3 faden (doesn't claim to be a gwindel)
4 bad shot (doesn't claim to be a gwindel)

Last night it did... but the description has apparently been changed overnight. For 3 it said to be a combination of faden and gwindel, which it is not. And for 4 it said there was a small gwindel in front of the largest crystal, which I couldn't see, they changed gwindel into fadenquartz, but I actually can't see a fadenquartz either.....

8 gitterquartz, as written (doesn't claim to be a gwindel)

They also changed this one overnight. It used to say that they were either gwindels or twins.

Thanks for changing the descriptions Rob or Tim, I appreciate that. But whenever you think that my comments are questionable, feel free to contact me and argue with me. I'm quite often wrong winking smiley

what is a "transitional gwindel"???

Beats me, totally new concept to me winking smiley



Edited 2 time(s). Last edit at 09/14/2011 07:28AM by Harjo Neutkens.
Timothy Blackwood September 14, 2011 04:15PM
Hi Harjo,

You're most welcome. And thank you for bring the questioned photos to my attention. :) Upon seeing the list you provided I went through and made the necessary corrections. For the 4th photo on the list I went back and added additional photos showing the smaller crystal that was thought to be a gwindel (in the close-ups), as well as another full-view photo taken from a different angle. It appears to show just normal parallel growth, but I just wanted to highlight the area of the specimen for those who might wish to see it in greater detail. Thanks again. I've learned much from re-examining the photos in the light of your comments. Unfortunately, true gwindels are specimens I have little experience with.

Best wishes,
Cohasset, MN, USA
Harjo Neutkens September 14, 2011 07:15PM
Well Tim, you're most welcome. And by providing the close-ups I can see a true gwindel on that specimen smiling smiley
Actually, the specimen seems to have more then one gwindel, I see at least two, maybe three typically gwindel-like twisted crystals. Nice specimen!
So that one will remain on the gwindel list.



Edited 1 time(s). Last edit at 09/14/2011 07:35PM by Harjo Neutkens.
Amir C. Akhavan September 14, 2011 09:00PM
Harjo Neutkens Wrote:
> Well Tim, you're most welcome. And by providing
> the close-ups I can see a true gwindel on that
> specimen smiling smiley

Hmm, where?
Harjo Neutkens September 14, 2011 09:38PM
Well, I think this is a gwindel.

Quite sure.

And maybe here's one too.

Not 100% sure though.

Edited 1 time(s). Last edit at 09/14/2011 09:39PM by Harjo Neutkens.
open | download - gwindel1.jpg (121.7 KB)
open | download - gwindel.jpg (95.1 KB)
Timothy Blackwood September 14, 2011 10:32PM
Hi Harjo,

I'm glad to have been able to help. :) I may be wrong, but I think the crystal you pointed to with a red arrow on the second full-specimen shot may be the same crystal as in the close-ups. But it does seem to be a gwindel.

Best wishes,
Cohasset, Minnesota, USA
Amir C. Akhavan September 14, 2011 10:44PM
There is a characteristic and "diagnostic feature" seen in many gwindels:
the edge between the prism faces is more twisted than the gwindel itself.
One can only see that in a top view.
If the edge is perfectly parallel to the other edges, one should double and triple check the specimen before making a claim.

The attached photo shows a top view of a clockwise twisted gwindel.

Edited 1 time(s). Last edit at 09/14/2011 10:45PM by Amir C. Akhavan.
open | download - gwindel_faces_2_scl.jpg (284.1 KB)
Timothy Blackwood September 16, 2011 03:57AM
Hello Amir,

Thank you for the excellent photos. They clearly illustrate the diagnostic twisting of the gwindel. :)

Best wishes,
Tim Blackwood
Cohasset, Minnesota, USA
Harjo Neutkens September 16, 2011 07:09AM
Tim, here are more interesting drawings and photos of gwindels: Amir's quartz-page:
Timothy Blackwood September 16, 2011 08:56AM
Hi Harjo,

Thank you very much for the link. It is most interesting. :)

Best wishes,
Cohasset, Minnesota, USA
falk burger October 16, 2011 02:52AM
happened to come across your chat as I was researching the likely nature of this crystal from Brazil. I see a lot of quartz and this is unique to my experience. What do you think?

open | download - IMG_0387.jpg (105.4 KB)
Rock Currier October 17, 2011 12:58AM
What features of the crystal do you find unique?

Rock Currier
Crystals not pistols.
falk burger October 18, 2011 05:01PM
rock currier,
I was looking for a knowledgeable opinion, preferably from Harjo as he seems to know his subject. If you can't see what's unique about this crystal, I'm not hopeful your opinion will add to my understanding.
Amir C. Akhavan October 18, 2011 05:56PM
@Falk Burger
This is an open forum, and everybody is invited to ask questions, show photos and also reply to questions, as long as one follows netiquette rules.

If you seek advice of a particular person, and don't want to hear opinions of others, you should contact that person via P.M. or email.

If you ask a question in a forum, it is perfectly o.k. for others to ask for clarification, as Rock has done, because it is meant to help finding the correct answer and to avoid misunderstandings.

I would advise to explain what you find unique about the crystal.
Harjo Neutkens October 18, 2011 07:04PM
Rock is way more knowledgeable than I am!
Rock asked you what you think is unique about the Quartz, so do I. I'd have to see a better picture of it.
Apart from that, I think your reaction on Rocks reply was not polite.

Edited 2 time(s). Last edit at 10/18/2011 07:56PM by Harjo Neutkens.
falk burger October 30, 2011 08:43PM
So the redoubtable Harjo Neutkens AND the truly stupefying Amir Akhavan (whose quartz info pages are enlightening and contributed much to my understanding - my sincere thanks) can't see what's so unusual about the crystal? Seems to me you're either not as knowledgeable as I thought or adopting a disingenuous posture of false humility in order to police my forthrightness which you find impolite. Duly noted. Your defense of the hapless rock currier is noble and must preempt anything so fatuous as the exchange of pertinent info. Please forgive the sarcasm but seriously? None of you can see the twistal in that crystal? I'm going to stick with calling a spade what it is - if etiquette is your paramount value, where are you? The violence you do to free discourse -and to me- is far greater than the simple slight with which I invited rock currier to have another look. In a discussion of "questionable gwindels" - really!
Harjo Neutkens October 30, 2011 09:42PM
First; Amir immediately recognized the twist, and we talked about it. I also see something that looks like a twist, albeit not like in a gwindel.
Second, Rock is far, far more knowledgeable than I am, really!
Third, I think we got of on a wrong start here. So let's bury the hatchet (if there ever was one winking smiley and talk about the crystal, because we are genuinely interested.
If you post a couple more detail photos we can discuss the crystal further. To judge what it is I really need more photos, in order to rule out the possibility that it is a rehealed crystal.


falk burger October 31, 2011 05:40PM
Thanks, Harjo, you're a gent.
my attitude is, it's not about us, it's all about the crystals. We're just here to be awed by them - I'm sure Rock saw the twist, he was prolly just feeling chatty and I was not. Depending on the time of day, I can get a bit cranky about how much time I spend at the computer when I have rocks to polish - Tucson is always closer than I think. Here are two more pictures, I failed to attach the others but will do so at your request, also special angles or closeups if you like. One sometimes sees very faint C-axis twist in prismatic habit crystals, but this one stands out with a dramatic twist on all six prism faces and good continuity from termination to term. Of course I have high hopes this might be one of the very rare C-axis gwindels, but I'm not holding my breath.


open | download - IMG_0386.jpg (30.7 KB)
open | download - IMG_0385.jpg (31.1 KB)
Harjo Neutkens October 31, 2011 06:40PM
Thanks for the photos. The twist is much more prominent than I thought to be seeing in the first photo.
It sure looks very uncommon. As for now I'm afraid I haven't got a conclusive answer as to what governs the twist.
First I thought a bent Quartz rather than a twisted Quartz could be an option, but I've never seen Quartz bent around the c-axis, but then again, I haven't seen lots of things yet.... Looking at it it though the twist seems to be very consistent, almost too consistent for a bent crystal, so it might be a twisted Quartz crystal. Difficult one winking smiley
falk burger November 03, 2011 03:39PM
As I research this further, it appears there are two crystals in parallel but slightly out-of-phase growth that is causing the twist. I'll consult Dana vol.3, as a friend suggested, for the proper terminology and further insight into how this happens. Please keep in touch about anything you may want to add..

Joseph Polityka November 03, 2011 04:32PM

This is the best photo I could get of the top view of the quartz from Branchville, Connecticut.

Regardless, it is a rare locality specimen.


Amir C. Akhavan November 03, 2011 11:52PM
Joe, I can't see anything that would indicate a gwindel.
Looks more like 2 intergrown flat crystals that are slightly rotated with respect to each other.
I can't see any x faces, too.
Joseph Polityka November 04, 2011 01:54AM

Thank you; I will change the information on my Mindat photo.

Best wishes,

Robert Simonoff February 26, 2012 01:44AM
We just posted this to the mindat photo gallery, but would love to have confirmation that it is indeed a gwindel. It is from Giuv Valley, Tujetsch (Tavetsch), Vorderrhein Valley, Grischun (Grisons; Graubünden), Switzerland. Note we have no reason to doubt it, but it would be nice to have expert confirmation.

Side View

Looking down the top

Ralph Bottrill February 26, 2012 05:35AM
Looks like parallel crystals with a systematic twist, so yes.

Andy Stucki (2) February 26, 2012 09:07AM
Even if I am very late with my contribution, I couldn't help but enter the discussion on one of my home topics.
Going back to the first few posts, I agree with Amir almost all the way and may be able to answer a question of his.
One or two remarks, though: Numbers 13 and 14 are not clear on the photo, I would need a top view, too. These being gwindels is probable, though, as both localities are well known for producing quite a few gwindels.
No. 15 sure looks like a gwindel to me. Again, locality is known for gwindels and the piece just looks right.

About "transitional" gwindels: I think it's not a truly official term. What you often observe in gwindel-rich environments are a number of classic " flat-lying" gwindels (C-axis more or less parallel to cleft walls) and often a few gwindels that look like a hybrid between a classic gwindel and a single, upright point. You will see some (but not much) rotation and just a little stacking along C-axis. Kind of hard to describe. Let me go though my photo files and post a decent picture soon.

As for Falk's quartz (if you are interested in my opinion), I am not yet sure at what I am looking at. I can't recognize a diagnostic twist. I may need a top view (in this case, side view).

Andy Stucki (2) February 26, 2012 09:16AM
Two more things:
I'm very tempted to label Joseph's Connecticut piece as a "closed gwindel" (there seems to be some twist). However, I am not familiar with the geology in Branchville to say that this would make sense.
Jessica and Robert's piece is a gwindel, no doubt. What I do question, however, is the locality. This looks more like one of the new Cavradi gorge gwindels than a Giuv Valley piece. the light color, the thinness and the "openness" point away from the Giuv Valley. (By the way: The mistake wouldn't be dramatic, it's just a gorge opposite the Giuv Valley). But then again, the Giuv Valley has produced a variety of gwindels.

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