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Improving Mindat.orgQuestionable gwindels
13th Sep 2011 21:30 UTCHarjo Neutkens Manager
There are a few of which I'm not sure if they are actually gwindels.
Please feel free to correct me (especially Amir :-)
http://www.mindat.org/photo-306994.html http://www.mindat.org/photo-318581.html normal parallel growth
http://www.mindat.org/photo-196056.html not a combination of fadenquartz with a gwindel; fadenquartz only
http://www.mindat.org/photo-291286.html difficult to see, but I'm not sure there's a gwindel in the cluster
http://www.mindat.org/photo-228878.html not a combination of fadenquartz with a gwindel; fadenquartz only
http://www.mindat.org/photo-361654.html not sure, doesn't look twisted, so maybe normal parallel growth
http://www.mindat.org/photo-277949.html rehealed Quartz crystals
http://www.mindat.org/photo-168090.html "Gitterquarz" (oriented growth on Feldspar)
http://www.mindat.org/photo-410310.html very good gwindel disguise. But I think it's normal parallel growth (gwindel in pegmatite is unlikely)
http://www.mindat.org/photo-411346.html normal parallel growth
http://www.mindat.org/photo-410212.html I think normal parallel growth
http://www.mindat.org/photo-154848.html not sure....
http://www.mindat.org/photo-160004.html not sure, but I think normal parallel growth
http://www.mindat.org/photo-59101.html normal parallel growth
http://www.mindat.org/photo-396828.html normal parallel growth
http://www.mindat.org/photo-260443.html very good disguise, but I think it's not a gwindel (unlikely in a pegmatite).
http://www.mindat.org/photo-186172.html tiny one, I looked at it for hours under the microscope and I'm quite sure it's a gwindel, but not 100% sure
Cheers,
Harjo
14th Sep 2011 02:02 UTCAmir C. Akhavan Expert
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 ;-) You should be able to tell, need top view photo
For 9, check description of locality http://www.mindat.org/loc-2534.html
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.
14th Sep 2011 08:21 UTCHarjo Neutkens Manager
3 faden (doesn't claim to be a gwindel)
4 bad shot (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 ;-)
what is a "transitional gwindel"???
Beats me, totally new concept to me ;-)
Cheers,
Harjo
14th Sep 2011 17:15 UTCTimothy Blackwood
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,
Tim
Cohasset, MN, USA
14th Sep 2011 20:15 UTCHarjo Neutkens Manager
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.
Cheers,
Harjo
14th Sep 2011 22:00 UTCAmir C. Akhavan Expert
-------------------------------------------------------
> Well Tim, you're most welcome. And by providing
> the close-ups I can see a true gwindel on that
> specimen :-)
Hmm, where?
14th Sep 2011 22:38 UTCHarjo Neutkens Manager
Quite sure.
And maybe here's one too.
Not 100% sure though.
14th Sep 2011 23:32 UTCTimothy Blackwood
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,
Tim
Cohasset, Minnesota, USA
14th Sep 2011 23:44 UTCAmir C. Akhavan Expert
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.
16th Sep 2011 04:57 UTCTimothy Blackwood
Thank you for the excellent photos. They clearly illustrate the diagnostic twisting of the gwindel. :)
Best wishes,
Tim Blackwood
Cohasset, Minnesota, USA
16th Sep 2011 08:09 UTCHarjo Neutkens Manager
16th Sep 2011 09:56 UTCTimothy Blackwood
Thank you very much for the link. It is most interesting. :)
Best wishes,
Tim
Cohasset, Minnesota, USA
16th Oct 2011 03:52 UTCfalk burger
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?
Falk
17th Oct 2011 01:58 UTCRock Currier Expert
18th Oct 2011 18:01 UTCfalk burger
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.
falk
18th Oct 2011 18:56 UTCAmir C. Akhavan Expert
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.
18th Oct 2011 20:04 UTCHarjo Neutkens Manager
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.
30th Oct 2011 20:43 UTCfalk burger
30th Oct 2011 21:42 UTCHarjo Neutkens Manager
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 ;-) 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.
Cheers,
Harjo
31st Oct 2011 17:40 UTCfalk burger
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.
Best,
Falk
31st Oct 2011 18:40 UTCHarjo Neutkens Manager
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 ;-)
3rd Nov 2011 15:39 UTCfalk burger
Falk
3rd Nov 2011 16:32 UTCJoseph Polityka Expert
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.
Best,
Joe
3rd Nov 2011 23:52 UTCAmir C. Akhavan Expert
Looks more like 2 intergrown flat crystals that are slightly rotated with respect to each other.
I can't see any x faces, too.
4th Nov 2011 01:54 UTCJoseph Polityka Expert
Thank you; I will change the information on my Mindat photo.
Best wishes,
Joe
26th Feb 2012 01:44 UTCRobert Simonoff
Thanks
Bob
26th Feb 2012 05:35 UTCRalph S Bottrill 🌟 Manager
26th Feb 2012 09:07 UTCAndy Stucki (2)
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
Switzerland
26th Feb 2012 09:16 UTCAndy Stucki (2)
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.
Cheers,
Andy
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