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Rarest quartz twins with inclined axes C
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Reef




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PostPosted: Oct 31, 2017 09:29    Post subject: Re: Rarest quartz twins with inclined axes C  

Hi Jordi. Thank you. Overlooked.

Another variant of the arrangement is in the twins of the Japanese type.
There was a splicing of prisms. A small crystal is located on the prism of a large crystal and partially submerged. The angle and parallelism of the faces correspond to the Japanese twinning law. Up to X - shape does not grow, absorption will take place. Maybe I missed something? Is this a Japanese twin ?



J.jpg
 Description:
Schematic drawing
Japan Law Twin
Variant 2
Lines show parallel edges (zone vectors). Crosses are parallel faces.
 Viewed:  663 Time(s)

J.jpg


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PostPosted: Nov 03, 2017 05:26    Post subject: Re: Rarest quartz twins with inclined axes C  

Can anyone confirm or disprove this opinion (previous message)? If such splices (a prism to a prism) do not contradict the laws of twinning, then the circle of search for twins will expand. And we can wait for new finds. This applies only to the analogues of the Japanese twins.

For a more in-depth study on this topic, I recommend reading Hans Grimmer "Quartz aggregates revisited"
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PostPosted: Nov 03, 2017 08:14    Post subject: Re: Rarest quartz twins with inclined axes C  

It may seem a small point but the proper name for the twin is Japan law twin, not Japanese twin. Japanese twins are properly represented in the attached image.


Twin.jpg
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Japanese twin
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Twin.jpg


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PostPosted: Nov 04, 2017 11:02    Post subject: Re: Rarest quartz twins with inclined axes C  

In http://www.mineral-forum.com/message-board/viewtopic.php?p=59449#59449 John S. White wrote:
It may seem a small point but the proper name for the twin is Japan law twin, not Japanese twin. Japanese twins are properly represented in the attached image.

So funny...😝
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PostPosted: Nov 04, 2017 11:02    Post subject: Re: Rarest quartz twins with inclined axes C  

I agree, pleasant twins.
The costs of machine translation. The main thing is for people to understand what the conversation is about.

Continue..
Goldschmidt law twin
Angle 47°43'



Goldschmidt law twin.jpg
 Description:
Schematic drawing
Goldschmidt law twin
Lines show parallel edges (zone vectors). Crosses are parallel faces.
 Viewed:  498 Time(s)

Goldschmidt law twin.jpg



82.jpg
 Mineral: Quartz
 Locality:
Alatau, Bashkortostan Republic, Southern Urals, Urals Region
 Dimensions: 14x9mm
 Description:
Goldschmidt law twin
 Viewed:  500 Time(s)

82.jpg



83 .jpg
 Mineral: Quartz
 Locality:
Alatau, Bashkortostan Republic, Southern Urals, Urals Region, Russia
 Dimensions: 14x9mm
 Description:
Goldschmidt law twin
 Viewed:  504 Time(s)

83 .jpg


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PostPosted: Nov 04, 2017 11:56    Post subject: Re: Rarest quartz twins with inclined axes C  

Breithaupt law twin
Angle 48°54'



Breithaupt.jpg
 Description:
Schematic drawing
Breithaupt law twin
Color lines show parallel edges (zone vectors). Crosses are parallel faces.
 Viewed:  468 Time(s)

Breithaupt.jpg


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PostPosted: Nov 04, 2017 12:01    Post subject: Re: Rarest quartz twins with inclined axes C  

Zwickau law twin
Angle 42°17'



Zwickau.jpg
 Description:
Schematic drawing
Zwickau law twin
Color lines show parallel edges (zone vectors). Crosses are parallel faces.
 Viewed:  466 Time(s)

Zwickau.jpg


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PostPosted: Nov 04, 2017 12:50    Post subject: Re: Rarest quartz twins with inclined axes C  

Friedel Law Twin
Angle 90°



3.jpg
 Mineral: Quartz
 Locality:
Alatau, Bashkortostan Republic, Southern Urals, Urals Region, Russia
 Dimensions: 14x9mm
 Description:
Friedel Law Twin
 Viewed:  455 Time(s)

3.jpg



DSCI7098.jpg
 Mineral: Quartz
 Locality:
Alatau, Bashkortostan Republic, Southern Urals, Urals Region, Russia
 Dimensions: 15x11mm
 Description:
Friedel Law Twin ?
 Viewed:  455 Time(s)

DSCI7098.jpg


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Josele




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PostPosted: Nov 04, 2017 13:59    Post subject: Re: Rarest quartz twins with inclined axes C  

Reef, thank you for sharing your schemes of these little known twins. Is a hard work to recognize them in practice because the need of very accurate measurements. My level in crystallography do not allows me to enter in a scientific discussion but anyway is interesting to know that they exist. Henceforth I will look at quartz aggregates carefully and with more interest.
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PostPosted: Nov 08, 2017 11:38    Post subject: Re: Rarest quartz twins with inclined axes C  

Yosele, good luck with your search !

Reichenstein - Griesernthal law twin



Gri.jpg
 Description:
Schematic drawing
Griesernthal law twin
Angle 76° 26'
Parallel faces of a rhombohedron on outside
 Viewed:  328 Time(s)

Gri.jpg



reich.jpg
 Description:
Schematic drawing
Reichenstein law twin
Angle 103°34'
Parallel faces of a rhombohedron on top
 Viewed:  327 Time(s)

reich.jpg



RG.jpg
 Description:
View from above
Reichenstein - Griesernthal law twin
Red lines for Griesernthal , blue lines for Reichenstein
 Viewed:  328 Time(s)

RG.jpg



1.jpg
 Mineral: Quartz
 Locality:
Alatau, Bashkortostan Republic, Southern Urals, Urals Region, Russia
 Dimensions: 10x8mm
 Description:
Reichenstein - Griesernthal law twin Double terminated twin Y-shape View from above
 Viewed:  328 Time(s)

1.jpg



1 (1).jpg
 Mineral: Quartz
 Locality:
Alatau, Bashkortostan Republic, Southern Urals, Urals Region, Russia
 Dimensions: 10x8mm
 Description:
Reichenstein - Griesernthal law twin Double terminated twin Y-shape View from above
 Viewed:  327 Time(s)

1 (1).jpg



2 (1).jpg
 Mineral: Quartz
 Locality:
Alatau, Bashkortostan Republic, Southern Urals, Urals Region, Russia
 Dimensions: 13x11mm
 Description:
Reichenstein - Griesernthal law twin
Double terminated
twin Y-shape
 Viewed:  328 Time(s)

2 (1).jpg



2.jpg
 Mineral: Quartz
 Locality:
Alatau, Bashkortostan Republic, Southern Urals, Urals Region, Russia
 Dimensions: 13x11mm
 Description:
Reichenstein - Griesernthal law twin
Double terminated
twin Y-shape
View from above
 Viewed:  326 Time(s)

2.jpg


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PostPosted: Nov 08, 2017 14:47    Post subject: Re: Rarest quartz twins with inclined axes C  

I came into this discussion a little late so please forgive me if this is something that has already been disclosed. What confuses me is that I see no mention of the goniometry that enabled the writer to determine the angles between the various crystals. My inclination when I see satellite crystals growing upon a large crystal in many different angles is to believe that if one of them is at an angle very close to a recognized twin angle, that is merely an accident and not a twin. So first, my question is how were these angles measured?
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PostPosted: Nov 08, 2017 15:33    Post subject: Re: Rarest quartz twins with inclined axes C  

John, I think that when two crystals grow over a matrix, many different forces interact. In contrary, when a second crystal grows over a face of a first crystal, its orientation depends mainly by atomic lattice. The same happens in phenocrystals floating in magma.
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PostPosted: Nov 08, 2017 19:05    Post subject: Re: Rarest quartz twins with inclined axes C  

Not an answer to my question.,
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PostPosted: Nov 08, 2017 19:25    Post subject: Re: Rarest quartz twins with inclined axes C  

I mean that often it can be a twin instead of an accident.
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PostPosted: Nov 08, 2017 19:58    Post subject: Re: Rarest quartz twins with inclined axes C  

marco campos-venuti wrote:
I mean that often can be a twin instead than an accident.


Marco, please tell us how you decide that a relationship between two individual crystals constitutes twinning - what is the definition of a twin, in your view? How does it differ from auto-epitaxy?

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PostPosted: Nov 08, 2017 20:27    Post subject: Re: Rarest quartz twins with inclined axes C  

I think auto-epitaxy is a synonym of twinning. Epitaxy is between two different minerals.
If a secondary xl (or a epitaxial film) grows over a main xl, its atoms will continue the lattice of the first. And they orientate following some laws. This is a twin.
The diagrams of reef look like epitaxy when he draws a small xl over a big one, but when he draws two xls of the same size they look more like twins. Isn't it?
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PostPosted: Nov 09, 2017 11:25    Post subject: Re: Rarest quartz twins with inclined axes C  

John S. White wrote:
... So first, my question is how were these angles measured?

If there is a parallelism of faces and edges, as in diagrams, then there is no doubt. It will be a twin. It remains only to make sure of the parallelism. Measuring the angle on a goniometer is sometimes more difficult than seeing the parallelism in a microscope. I additionally confirmed my samples on a goniometer.

to Pete Richards:
Maybe this quote from Wikipedia will clarify: "Some authors[18] consider that overgrowths of a second generation of the same mineral species should also be considered as epitaxy, and this is common terminology for semiconductor scientists who induce epitaxic growth of a film with a different doping level on a semiconductor substrate of the same material. For naturally produced minerals, however, the International Mineralogical Association (IMA) definition requires that the two minerals be of different species.[19]"
When homoepitaxy occurs, the crystal itself grows or the next generation occurs with the same orientation of the crystal lattice.
Twins are a regular, nonparallel fusion of crystalline individuals of a single mineral.
The formation of twins is determined by the properties of the lattice of the crystal, and occurs according to strictly defined laws.
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PostPosted: Nov 14, 2017 07:57    Post subject: Re: Rarest quartz twins with inclined axes C  

Thanks for your tips dear friend, like when getting a hand of help here!
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