We use cookies to show content based on your preferences. If you continue to browse you accept their use and installation. More information. >

FMF - Friends of Minerals Forum, discussion and message board
The place to share your mineralogical experiences

FMF English Forum is moderated by John S. White and Peter Megaw
 

Spanish message board






Newest topics and users posts
24 May-03:12:51 The mizunaka collection - rhodochrosite (Am Mizunaka)
24 May-00:54:17 Re: collection of heimo hellwig (Heimo Hellwig)
23 May-22:35:53 Re: new mexico collecting - (27) (Philip Simmons)
23 May-16:52:55 Re: please help identify (Kevin Schofield)
23 May-16:42:22 Re: please help identify (Southernappalachian)
23 May-16:02:44 Re: please help identify (Kevin Schofield)
23 May-15:26:40 Please help identify (Southernappalachian)
23 May-14:41:14 Re: the mizunaka collection - quartz (Am Mizunaka)
23 May-10:24:44 Re: collection of dontgogreen (Dontgogreen)
23 May-03:52:50 Re: the mizunaka collection - quartz (Pierre Joubert)
23 May-00:54:59 Re: please identify - rock with white inclusions (Foreman)
22 May-19:38:51 The mizunaka collection - quartz (Am Mizunaka)
22 May-19:09:44 Re: please identify (Peter Megaw)
22 May-05:24:34 Re: collection of heimo hellwig (Heimo Hellwig)
21 May-23:04:25 Re: franjungle collection (Franjungle)
21 May-21:05:00 The mizunaka collection - rhodochrosite (Am Mizunaka)
20 May-21:35:31 The mizunaka collection - quartz (Am Mizunaka)
20 May-21:14:36 Re: please identify (Peter Lemkin)
20 May-20:23:31 Re: please identify (Dale Hallmark)
20 May-20:19:36 Re: please identify (Dale Hallmark)
20 May-18:32:23 Re: please identify (Josele)
20 May-17:57:22 Re: breakfast with minerals - podcast discussion - episode 01 (Turbo)
20 May-17:46:12 Please identify (Vcollector)
20 May-17:30:55 Re: breakfast with minerals - podcast discussion - episode 01 (Dave Waisman)
20 May-13:36:47 Re: what is that mineral (Ivital)

For lists of newest topics and postings click here


RSS RSS

View unanswered posts

Why and how to register

Index Index
 FAQFAQ RegisterRegister  Log inLog in
 {Forgotten your password?}Forgotten your password?  

Like
42751


The time now is May 24, 2018 05:13

Search for a textSearch for a text   

A general guide for using the Forum with some rules and tips
Unsure about Japan law twin, please help.
  
  Index -> FOR BEGINNERS: What is it? Where is it from?
Like
8


View previous topic :: View next topic  
Author Message

Ricardo Melendez




Joined: 21 Apr 2014
Posts: 65
Location: Estado de Mexico


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 16, 2018 17:35    Post subject: Unsure about Japan law twin, please help.  

Hi, just yesterday I noted V shape in a quartz cluster from Charcas, SLP, México.

And remember about Japan law twins, then try to measure the angle but most the time I get a result lightly above 85 degrees.

There is any chance that this specimen is a Japan law twin?



IMG_8930.JPG
 Mineral: Quartz
 Description:
Quartz cluster partially altered to limonite
 Viewed:  2056 Time(s)

IMG_8930.JPG



IMG_8929.JPG
 Mineral: Quartz
 Description:
 Viewed:  2053 Time(s)

IMG_8929.JPG



IMG_8928.JPG
 Mineral: Quartz
 Description:
 Viewed:  2053 Time(s)

IMG_8928.JPG



IMG_8942.JPG
 Mineral: Quartz
 Description:
 Viewed:  2056 Time(s)

IMG_8942.JPG


Back to top
Reply to topic Reply with quote
Like
1
   

John Betts




Joined: 07 Jun 2012
Posts: 104
Location: New York City

View user's profile

Send private message

PostPosted: Jan 16, 2018 17:43    Post subject: Re: Unsure about Japan law twin, please help.  

It looks like a Japan Law twin to me. There might be a second twin resting on your thumb in the two lower photos.
_________________
John Betts
Back to top
Reply to topic Reply with quote
Like
1
   

alfredo
Site Admin



Joined: 30 Jan 2008
Posts: 693
Location: New York


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 16, 2018 18:19    Post subject: Re: Unsure about Japan law twin, please help.  

I agree with John, almost certainly a Japan-law twin. Nice find.
Back to top
Reply to topic Reply with quote
Like
1
   

Max Merlo




Joined: 16 Jan 2018
Posts: 3
Location: Torino

View user's profile

Send private message

PostPosted: Jan 16, 2018 18:26    Post subject: Re: Unsure about Japan law twin, please help.  

I've tried to measure the angle from last pic,
I'm also agree about Japan-twin


Max



japan-twin.jpg
 Description:
 Viewed:  2015 Time(s)

japan-twin.jpg


Back to top
Reply to topic Reply with quote
Like
1
   

Ricardo Melendez




Joined: 21 Apr 2014
Posts: 65
Location: Estado de Mexico


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 16, 2018 18:32    Post subject: Re: Unsure about Japan law twin, please help.  

thanks a lot guys for your expert opinion always much appreciated.
Back to top
Reply to topic Reply with quote
Like
   

Harjo




Joined: 04 Nov 2009
Posts: 31
Location: Vessem


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 16, 2018 19:09    Post subject: Re: Unsure about Japan law twin, please help.  

I'm not that sure. The fact that the prism faces are not in the same plane makes me a bit hesitant... I think it's a sidecar crystal that happens to sit on the other crystal at roughly the angle of a Japan law twin.
Back to top
Reply to topic Reply with quote
Like
   

John Betts




Joined: 07 Jun 2012
Posts: 104
Location: New York City

View user's profile

Send private message

PostPosted: Jan 16, 2018 19:25    Post subject: Re: Unsure about Japan law twin, please help.  

The second photo shows the prism faces are parallel.
_________________
John Betts
Back to top
Reply to topic Reply with quote
Like
   

Harjo




Joined: 04 Nov 2009
Posts: 31
Location: Vessem


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 16, 2018 19:28    Post subject: Re: Unsure about Japan law twin, please help.  

Yes, but not in the same plane.
Back to top
Reply to topic Reply with quote
Like
   

John S. White
Site Admin



Joined: 04 Sep 2006
Posts: 1224
Location: Stewartstown, Pennsylvania, USA


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 16, 2018 21:13    Post subject: Re: Unsure about Japan law twin, please help.  

The prism faces are certainly in the same plane. The only correction I would make with the original description is that the quartz is not being replaced, it is coated with a secondary mineral.
_________________
John S. White
aka Rondinaire
Back to top
Reply to topic Reply with quote
Like
1
   

Harjo




Joined: 04 Nov 2009
Posts: 31
Location: Vessem


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 17, 2018 03:45    Post subject: Re: Unsure about Japan law twin, please help.  

Maybe I wasn't clear enough what I meant when I wrote "in the same level"
I didn't mean that they are not oriented (more or less) the same way, which they obviously are, what I meant is that both crystals don't share the same flat surface for the the prism faces, in other words, the main crystal's prism face protrudes compared to the other one.
I hope you understand what I try to say ;-) Usually in such a case, at least most of the material I've examined, such crystals that looked deceivingly much like a jap twin proved to be oriented growth but not twinned.
In order to be sure you need a photo of the cleaned cluster so you can see the twinning plane and striations on the prism faces.
My bet is still that it's not a Japan law twin, but if proven otherwise I'll gladly stand corrected.
Back to top
Reply to topic Reply with quote
Like
   

John S. White
Site Admin



Joined: 04 Sep 2006
Posts: 1224
Location: Stewartstown, Pennsylvania, USA


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 17, 2018 05:39    Post subject: Re: Unsure about Japan law twin, please help.  

Okay Harjo I now understand what you are referring to but I don't agree with you. The best example I have is Japan law twinned amethystine quartz from Madagascar where the front prism planes are not on the same level. They are, of course, coplanar.
_________________
John S. White
aka Rondinaire
Back to top
Reply to topic Reply with quote
Like
   

Harjo




Joined: 04 Nov 2009
Posts: 31
Location: Vessem


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 17, 2018 06:07    Post subject: Re: Unsure about Japan law twin, please help.  

I understand John, and I've been looking at a fair bit of Madagascar Jap law twins we have in our database at Mindat. What I can see is that in some cases there is alternative stepping between the two twinned crystals but always along the twinning plane, but not like we see in the crystals we discuss here. https://www.mindat.org/gallery.php?cform_is_valid=1&loc=2247&min=198&photoclass=1&showtype=1&orderxby=&cf_pager_page=4
All the edges in the Madagascar twins join at exactly the right spot, another feature that is not present in the crystals we discuss here. Take a close look at the photograph of the alleged twin taken from the top.
When looking for more Japan law twins from Madagascar I found one on ebay that is definitely not a Japan law twin ;-) See the attached photo.
If I see a photo of the cleaned cluster I can say for sure if it's a twin or not.



no jap law.jpg
 Mineral: quartz
 Description:
 Viewed:  1831 Time(s)

no jap law.jpg


Back to top
Reply to topic Reply with quote
Like
   

Dennis Beals




Joined: 06 Jan 2011
Posts: 13
Location: Denver

View user's profile

Send private message

PostPosted: Jan 18, 2018 18:55    Post subject: Re: Unsure about Japan law twin, please help.  

Hello
I have seen Japan Law crystals from Charcas but not with the sulphide coatings
Back to top
Reply to topic Reply with quote
Like
1
   

Bob Morgan




Joined: 18 Jan 2018
Posts: 2
Location: Savannah, Georgia

View user's profile

Send private message

PostPosted: Jan 18, 2018 23:34    Post subject: Re: Unsure about Japan law twin, please help.  

A quite accurate method of checking the twin comes from two sets of parallel pyramidal faces on the outside of the twin. A Vernier caliper should do.


J-Law confirm 2.JPG
 Mineral: Quartz Japan Law twin
 Locality:
Peñas Blancas Mine, Municipio San Pablo de Borbur, Western Emerald Belt, Boyacá Department, Colombia
 Dimensions: 3 cm across
 Description:
 Viewed:  1606 Time(s)

J-Law confirm 2.JPG



J-Law confirm 2.JPG
 Mineral: Quartz Japan Law twin
 Locality:
Peñas Blancas Mine, Municipio San Pablo de Borbur, Western Emerald Belt, Boyacá Department, Colombia
 Dimensions: 3 cm across
 Description:
 Viewed:  1608 Time(s)

J-Law confirm 2.JPG



J-Law Confirm 1.JPG
 Mineral: Quartz Japan Law twin
 Locality:
Peñas Blancas Mine, Municipio San Pablo de Borbur, Western Emerald Belt, Boyacá Department, Colombia
 Dimensions: 3 cm across
 Description:
 Viewed:  1617 Time(s)

J-Law Confirm 1.JPG


Back to top
Reply to topic Reply with quote
Like
1
   

Roger Warin




Joined: 23 Jan 2013
Posts: 848


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Jan 19, 2018 11:43    Post subject: Re: Unsure about Japan law twin, please help.  

Hello,
Here is a beautiful twin from La Gardette (Alps) as the French call it.
It is synonymous with Japan's twin. Specimens that assemble undeformed and well developed crystals are rare.
This twin corresponds to one of Clifford Frondel's drawings, Dana Vol. III, p. 92 (1962).



Quartz-1b_R.jpg
 Description:
 Viewed:  1522 Time(s)

Quartz-1b_R.jpg


Back to top
Reply to topic Reply with quote
Like
1
   
Display posts from previous:   
   Index -> FOR BEGINNERS: What is it? Where is it from?   All times are GMT - 5 Hours
Page 1 of 1
    

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


All pictures, text, design © Forum FMF 2006-2018


Powered by FMF