| View previous topic :: View next topic |
| Author |
Message |
Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5050
Location: Barcelona
|
|
| Back to top |
|
 |
Peter Farquhar
Site Admin
Joined: 14 May 2011
Posts: 52
Location: Virginia
|
 Posted: Dec 15, 2012 16:07 Post subject: Re: About cyclic twinning - (5) |
|
|
I enjoyed Duncan’s recent photo of the complex twin of adularia, as well as his detailed analysis and enlightening diagrams that unlock this twinning puzzle. Very nicely done.
In turn, I want to share a rare (unaltered) photo illustrating cyclic twinning in humans. Best wishes for a magical holiday season from the five of us.
Peter
| Description: |
Cyclic Twins
Los Angeles, California USA
Rare example of five-fold cyclic twinning in humans captured by John Gaughan at his magic shop in Los Angeles on November 7, 2009. |
|
| Viewed: |
41595 Time(s) |
|
|
|
| Back to top |
|
|
Pete Richards
Site Admin
Joined: 29 Dec 2008
Posts: 845
Location: Northeast Ohio
|
| Posted: Dec 15, 2012 16:33 Post subject: Re: About cyclic twinning - (5) |
|
|
Most remarkable! The individuals of this complex twin are not even in contact with each other - a non-contact fiveling!
_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy |
|
| Back to top |
|
|
Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5050
Location: Barcelona
|
| Posted: Dec 15, 2012 16:54 Post subject: Re: About cyclic twinning - (5) |
|
|
| Pete Richards wrote: | | ...The individuals of this complex twin are not even in contact with each other.... |
Maybe better.... ;-) ;-)
|
|
| Back to top |
|
|
domenico
Joined: 31 Dec 2012
Posts: 28
Location: Garbagnate Mil.-Italy
|
| Posted: Dec 31, 2012 07:36 Post subject: Re: About cyclic twinning - (5) |
|
|
My little contribution for this good topic...
Sorry for having only an old "diapositive" digitalyzed but the sample is not in my collection.
| Description: |
Rutile
Crevoladossola quarries, Ossola Valley-Italy
1 mm
Photo B.Turconi
Colleection P.Barili |
|
| Viewed: |
41164 Time(s) |
|
|
|
| Back to top |
|
|
Peter Farquhar
Site Admin
Joined: 14 May 2011
Posts: 52
Location: Virginia
|
| Posted: Jan 02, 2013 20:24 Post subject: Re: About cyclic twinning - (5) |
|
|
Please let everyone know that the human cyclic twins shown in my earlier photo really are in constant contact with each another (unlike some other family members with whom we’ve lost close contact). While the earlier photo does not reveal everything, as Jordi suggested it’s better to forego more details.
On a more serious note, I’d appreciate any help in deciphering the twinning in an old rutile specimen (PF-3205) from Minas Gerais, Brazil. Photo “A” shows multiple V-twinning on the front side of this rutile specimen. What else can be said to further describe this complex crystal?
Likewise photo “B” shows many terminations on the top of this stout rutile specimen. What more can you say about these terminations and this specimen? Thanks.
Peter Farquhar
Claremont, California
USA
| Description: |
Rutile "A" (PF-3205)
Minas Gerais, Brazil
5.4 x 3.7 x 2.7 cm
A stout, extremely-well terminated, multiply twinned rutile crystal. Front view. |
|
| Viewed: |
42706 Time(s) |
|
| Description: |
Rutile "B" (PF-3205)
Minas Gerais, Brazil
5.4 x 3.7 x 2.7 cm
A stout, extremely-well terminated, multiply twinned rutile crystal. Top view. |
|
| Viewed: |
42691 Time(s) |
|
|
|
| Back to top |
|
|
Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
|
| Posted: Jan 03, 2013 11:12 Post subject: Re: About cyclic twinning - (5) |
|
|
Another cyclic twinned rutile from Georgia:
| Description: |
Rutile
Graves Mountain, Lincoln County, Georgia, USA
6 x 6 x 5 cm
Photo and collection: Pep Gorgas |
|
| Viewed: |
42684 Time(s) |
|
_________________
Josele |
|
| Back to top |
|
|
Peter Farquhar
Site Admin
Joined: 14 May 2011
Posts: 52
Location: Virginia
|
| Posted: Jan 05, 2013 12:41 Post subject: Re: About cyclic twinning - (5) |
|
|
| Josele wrote: | | Another cyclic twinned rutile from Georgia: |
Very interesting and unusually sharp cyclic twin from Graves Mountain. Thanks for posting this photo.
Do you have other photos of this rutile specimen from different angles?
|
|
| Back to top |
|
|
Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
|
| Posted: Jan 05, 2013 15:21 Post subject: Re: About cyclic twinning - (5) |
|
|
| RutileFox wrote: | | ... Do you have other photos of this rutile specimen from different angles? |
I asked for more pictures to Pep Gorgas, who is the owner of this >30 years old specimen and posted this picture in Spanish FMF, asking if somebody can trespass to here. I hope he will add more photos soon...
_________________
Josele |
|
| Back to top |
|
|
domenico
Joined: 31 Dec 2012
Posts: 28
Location: Garbagnate Mil.-Italy
|
| Posted: Jan 06, 2013 03:17 Post subject: Re: About cyclic twinning - (5) |
|
|
Again a little contribution using a good Chinellato Matteo photo...
| Description: |
Rutile
Diamantina, M.G. Brazil
10,8 mm
Photo Matteo Chinellato
Collection Domenico Preite |
|
| Viewed: |
42573 Time(s) |
|
_________________
User Mindat Gallery:
----------------------------
http://www.mindat.org/user-6983.html#0 |
|
| Back to top |
|
|
Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
|
| Posted: Jan 06, 2013 08:17 Post subject: Re: About cyclic twinning - (5) |
|
|
| Josele wrote: | | I asked for more pictures to Pep Gorgas, ... |
Here they are:
| Description: |
Rutile
Graves Mountain, Lincoln County, Georgia, USA
6 x 6 x 5 cm
Photo and collection: Pep Gorgas |
|
| Viewed: |
42530 Time(s) |
|
| Description: |
Rutile
Graves Mountain, Lincoln County, Georgia, USA
6 x 6 x 5 cm
Photo and collection: Pep Gorgas |
|
| Viewed: |
42435 Time(s) |
|
| Description: |
Rutile
Graves Mountain, Lincoln County, Georgia, USA
6 x 6 x 5 cm
Photo and collection: Pep Gorgas |
|
| Viewed: |
42471 Time(s) |
|
| Description: |
Rutile
Graves Mountain, Lincoln County, Georgia, USA
6 x 6 x 5 cm
Photo and collection: Pep Gorgas |
|
| Viewed: |
42462 Time(s) |
|
_________________
Josele |
|
| Back to top |
|
|
Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
|
| Posted: Jan 06, 2013 08:28 Post subject: Re: About cyclic twinning - (5) |
|
|
Here I add my own contribution: a multiple contact twin on {101} of cassiterite with some small quartz points and a bit of matrix.
| Description: |
Cassiterite
Viloco Mine (Araca mine), Loayza Province, La Paz Department, Bolivia.
4 x 3 x 2 cm. |
|
| Viewed: |
42443 Time(s) |
|
_________________
Josele |
|
| Back to top |
|
|
James Catmur
Site Admin
Joined: 14 Sep 2006
Posts: 1470
Location: Cambridge
|
| Posted: Jan 12, 2013 07:24 Post subject: Re: About cyclic twinning - (5) |
|
|
A contribution I spotted yesterday in the museum in Copenhagen, with a hole in the center and a nice model too. Two photos, one of the specimen and model and one with a bit more detail so that you can see the hole in the middle
| Description: |
Rutile
Magnet Cove, Akansas, USA
3 cm x 1cm |
|
| Viewed: |
42296 Time(s) |
|
| Description: |
Rutile
Magnet Cove, Akansas, USA
3 cm x 1 cm
More detail so that one can clearly see the hole in the middle, as one can see tha matrix. |
|
| Viewed: |
42280 Time(s) |
|
|
|
| Back to top |
|
|
Dean Allum
Joined: 27 Jan 2010
Posts: 17
Location: Colorado
|
| Posted: Jan 12, 2013 16:12 Post subject: Re: About cyclic twinning - (5) |
|
|
James,
Nice post! That hole appears to be a flat spot in a concave recess. Do you know that it extends all the way through the specimen?
Pete,
A cyclic twin with a hole in the center (similar to the model just shown) could still be consistent with your theory... if the twin was subjected to isotropic etching after formation.
I guess there is also a slight chance that they could be remnants of a sagenite array similar to what you showed earlier.
Are there any real-world examples of a large "donut hole" similar to the model?
-Dean Allum
|
|
| Back to top |
|
|
domenico
Joined: 31 Dec 2012
Posts: 28
Location: Garbagnate Mil.-Italy
|
| Posted: Jan 13, 2013 01:57 Post subject: Re: About cyclic twinning - (5) |
|
|
James very nice sample of cyclic twinning rutile from Magnet Cove.....
Complimenti !!!!
_________________
User Mindat Gallery:
----------------------------
http://www.mindat.org/user-6983.html#0 |
|
| Back to top |
|
|
|
FAQ 
Register
Log in
Forgotten your password?
