Questionable gwindels

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

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..

Falk

Hi,

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

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.

Amir,

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

Best wishes,

Joe

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.



Thanks
Bob

Looks like parallel crystals with a systematic twist, so yes.

Regards,
Ralph

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
Switzerland

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.

Cheers,
Andy