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Waterclear mineral from Nepal?
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Jordi Fabre
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PostPosted: Jan 01, 2013 14:11    Post subject: Re: Waterclear mineral from Nepal?  

Is very easy to do a simple hardness test, the Albite don't scratch the glass. As we work only with photos it could confuse, the photos are 2D and the crystallographic measures prefer 3D ;-)

BTW, 50 years ago the mistakes happens frequently and they were corrected later by the modern analytic techniques. Ask to the Museums! ;-)
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PostPosted: Jan 01, 2013 14:43    Post subject: Re: Waterclear mineral from Nepal?  

Hello,

Do not have expertise in mineralogical devices but once a mineralogist helped me identify a polished nodule using a hand held light refractometer. I came away with the idea that when the choices are few such a devise may be useful. Given the size of the specimen perhaps it could be tested in this way, provided the minerals being considered differ significantly in their RI's.

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PostPosted: Jan 02, 2013 10:08    Post subject: Re: Waterclear mineral from Nepal?  

Josele, I too am convinced that your spectacular crystal is indeed albite, but I must disagree with your statement that plagioclase transparency has any relation to Ca content. Ca-rich plagioclases can be completely transparent, more than enough to use as gemstones, like for example bytownite from Mexico, or almost end-member anorthite from Japan.
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PostPosted: Jan 02, 2013 13:58    Post subject: Re: Waterclear mineral from Nepal?  

Thanks for all comments. I agree with all your opinions:
- is strange there is not any cleavage indicator, nor inner "phantoms" parallel to (001),
- is not possible to take accurate crystallographic measures just from pictures,
- a hardness test will help to narrow the possibilities,
- a refraction test should be very useful too.
Then we must wait to these test or analysis to be absolutely sure, scientifically sure. Nevertheless, perhaps you will agree that as there is very, very, very much possibilities that is albite, is acceptable to name it as albite when noting it is "visually crystallographically identified"

alfredo wrote:
Josele, I too am convinced that your spectacular crystal is indeed albite, but I must disagree with your statement that plagioclase transparency has any relation to Ca content. ....

Alfredo, yes, I was mistaken, I was confused with K-feldspars and perthite demixing, sorry. Thank you very much for correction.

This specimen is in Eric's house in Kathmandu. Eric collect only quartz and have not other minerals he can use to check hardness. As he is a mono-specie collector, he has not practice to identify other species doing some test.
Having in mind he have an intermittent internet connection and, moreover, one of these days he was going on a trip to the mountains, I think perhaps it will take some time to check the crystal... I will post here the results when available.

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PostPosted: Apr 09, 2013 12:10    Post subject: Re: Waterclear mineral from Nepal?  

At last there is a test result of this amazing specimen. The test was done in a Japanese gemological laboratory and gives a stunning result (for me): Quartz

I'm not a crystalography expert but I seem to observe that:
- The angles between faces are imposible in quartz (even at naked eye).
- Striation here is parallel to c axis, never seen in quartz.

I think there is a mistake in this test: They have analyzed the quartz supporting the albite crystal.
Or I'm completely wrong...

What you think about?
Very thanks for your opinion.

Can see Test result in a high resolution image here.


Can see HD photos of the specimen here.



NippGemLab.jpg
 Description:
 Viewed:  13335 Time(s)

NippGemLab.jpg



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PostPosted: Apr 09, 2013 12:50    Post subject: Re: Waterclear mineral from Nepal?  

So tough to say from a picture but just at a glance if you said quartz for the support I would not blink. But if you say quartz for the clear mineral I would think about it twice or three times. I would try the hardness test as that is fairly indicative and you don't need a lab to do it.
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PostPosted: Apr 09, 2013 13:57    Post subject: Re: Waterclear mineral from Nepal?  

Dear Mark, thanks for your input. This piece is right now in Nepal and I am in Spain. The owner of the specimen is not expert in mineral testing and he do not want to damage this exceptional crystal. That's why he did not a hardness test himself.

Certainly, from a picture we can not do firm statements but spending some time to see the photos on the previous page, I can not recognize a quartz but it seems I'm wrong.

Perhaps somebody can help to clarify this matter.
Thanks for your comment.

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PostPosted: Apr 09, 2013 14:22    Post subject: Re: Waterclear mineral from Nepal?  

Good evening, Josele

I am maybe odd, but I thought always as Jordi.
An odd quartz (meaning odd that we are not used to see it; could be somehow abundant in some places)

I doubt that Japaneses analyzed the support.
I could not read Japanese, but they state " Nippon "gemstone" laboratory ".
If in a gem lab, I would analyze the "gem" portion.

Maybe I am wrong, but I should say that I am not surprised by the labo result.
Maybe I am too naive

With best wishes

Lluís
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PostPosted: Apr 09, 2013 15:12    Post subject: Re: Waterclear mineral from Nepal?  

How unfortunate that we cannot hold this crystal and twist it in any and all directions. If it is indeed quartz, there should be a set of six prism faces with parallel edges (well, part of the set might be missing), they should all have striations perpendicular to their parallel edges, and other faces should not be striated. If these could be identified, we could know the orientation of the crystal and perhaps understand the details of how it is distorted. I see striations on two faces, but cannot determine if they are all parallel or not.
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PostPosted: Apr 09, 2013 16:05    Post subject: Re: Waterclear mineral from Nepal?  

This has been very interesting. I think it points out the great difficulty in being certain of a "sight identification" of a crystal, especially when it is of an unusual habit and appearance.

I can certainly understand the reluctance to do a scratch test which might put excessive pressure on the specimen--being uncertain of how much stress the crystal could tolerate without snapping off. Especially when the handler is not terribly familiar with 'the feel" of exactly how to do a scratch test.

Wondering about the test by the Japanese lab--does it say anywhere, what method they actually used to make this identification? Just by sight and morphology? XRD? XRF? Something else? Many tests a lab might do would require removing a fragment from the specimen--again, I'm sure they would be reluctant to try to do this.

Looking at the photos, one keeps flip-flopping back and forth from the alternatives. The thin tabular overall shape, certainly looks like feldspar. But quartz can be tabular too--it COULD be quartz! Looking at the base of the crystal, it does not seem continuous with the quartz matrix--it looks like a separate growth of a different mineral. And so it goes! Here is one idea. If someone has access to photographing the specimen, perhaps they could also take a short video sequence—if a camera is available that can do this, close up with good resolution—showing the crystal as it is rotated and twisted to different positions. Such a video clip, sent to some of our crystal “experts” (Pete Richards, others), might lend some new insight. Just a thought.
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PostPosted: Apr 09, 2013 16:21    Post subject: Re: Waterclear mineral from Nepal?  

here is a non destructive idea that is not indicative but might give you a leg up. Try putting under a UV SW lamp (if you could find a three way lamp all the better. Feldspar can fluoresce dim red, especially if cold, then they often fluoresce brighter. I would doubt, if it were quartz, it would do anything (though I do have a La Sassa quartz that sure does fluoresce nicely!). Might try that. Won't hurt the crystal.
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PostPosted: Apr 09, 2013 18:14    Post subject: Re: Waterclear mineral from Nepal?  

Pete Richards wrote:
... If it is indeed quartz, there should be a set of six prism faces with parallel edges (well, part of the set might be missing), they should all have striations perpendicular to their parallel edges, and other faces should not be striated. If these could be identified, we could know the orientation of the crystal and perhaps understand the details of how it is distorted. I see striations on two faces, but cannot determine if they are all parallel or not.

Pete, thanks for your help. Following your reasoning, please see following pictures.


Pete Modreski wrote:
... Wondering about the test by the Japanese lab--does it say anywhere, what method they actually used to make this identification? Just by sight and morphology? XRD? XRF? Something else? Many tests a lab might do would require removing a fragment from the specimen--again, I'm sure they would be reluctant to try to do this. ...

Pete, I can't understand Japanese but I think the test was just optical. In paper results, test type are in English, I can read only RI result because is in numbers: 1,54 - 1,55.
I will ask Eric if he can take video.

Mark Ost wrote:
here is a non destructive idea that is not indicative but might give you a leg up. Try putting under a UV SW lamp (if you could find a three way lamp all the better. Feldspar can fluoresce dim red, especially if cold, then they often fluoresce brighter. ...

Mark, I think there is the fluorescence test result in the paper ...but in Japanese.

Very thanks for your inputs.



ab_GH6.JPG
 Description:
Presumed albite/quartz
Ganesh Himal, Dhading District, Bagmati Zone, Nepal
crystal size: 8,1 x 4,3 x 1,3 cm
Photo & collection: Eric Manandhar

I understand that the only position could exist a trigonal axis in this cristal should be in almost vertical position (in this photo), parallel to edges between presumed prism faces. But striation is also parallel...
 Viewed:  13117 Time(s)

ab_GH6.JPG



ab_GH5.JPG
 Description:
Presumed albite/quartz
Ganesh Himal, Dhading District, Bagmati Zone, Nepal
crystal size: 8,1 x 4,3 x 1,3 cm
Photo & collection: Eric Manandhar

Weird striations for a quartz...
 Viewed:  13103 Time(s)

ab_GH5.JPG



ab_GH3.JPG
 Description:
If we assume that quartz striation in prism faces are always perpendicular to c axis, in this picture we have trigonal axis in vertical position. Where are now the presummed edges between prism faces parallel to c axis?
 Viewed:  13113 Time(s)

ab_GH3.JPG



Q faden1.JPG
 Description:
Quartz
Miram Shah Tribal Area, North Waziristan, Pakistan
7 x 3 x 2 cm
In this tabular quartz is very easy to find c axis position using striation as a guide.
 Viewed:  13110 Time(s)

Q faden1.JPG



Q faden2.JPG
 Description:
Quartz
Miram Shah Tribal Area, North Waziristan, Pakistan
7 x 3 x 2 cm
Some of these Pakistani tabular faden quartz have amazing shapes, but using the striation is easy to find out c axis.
 Viewed:  13118 Time(s)

Q faden2.JPG



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PostPosted: Apr 09, 2013 19:05    Post subject: Re: Waterclear mineral from Nepal?  

With these extra images it appears that this could be a faden quartz crystal, which could help explain the unusual habit. And if this is true, it could have a nearly unique morphology because the direction of elongation of the vein is random with respect to the orientation of the initial quartz grain. So faden crystals in a given vein can look quite different from each other.

But, Josele, you did not say whether the last two images were from the same immediate locality as this specimen.

On the other hand, if it's a magnificent albite, there's no reason that other crystals from the cleft should not have similar morphology. Though faden albite is known, appealing to the faden mechanism is not helpful in interpreting this crystal in terms of albite morphology.

I'm beginning to weaken on the albite hypothesis! But we are still lacking important data. And I hate to be wrong!

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PostPosted: Apr 10, 2013 04:51    Post subject: Re: Waterclear mineral from Nepal?  

Last two images are of Pakistani quartz, not from Nepal as the presumed albite-quartz specimen. Yesterday I forget to indicate this in pictures, now is done.

Eric (the owner in Kathmandu) has read this thread and he said me that when the specimen comes back to Nepal from Japan he will take a video and more pictures to post here.

Also he translate from Japanese the test results:
RI: 1,54 - 1,55
"Polarized character is birefringence"
Not fluorescence under LW UV nor SW UV

Thanks again for your help.

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PostPosted: Apr 10, 2013 18:10    Post subject: Re: Waterclear mineral from Nepal?  

The puzzle continues--but the data do seem to be leaning more toward quartz. The r.i. difference is not large--albite should be around 1.53, and quartz of course, 1.54-1.55, which matches their reported value. I had also thought of mentioning fluorescence, since some (but not all) albite and orthoclase have at least a weak red fluorescence.

I guess personally--I'm inclining toward believing it to be quartz.
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PostPosted: Apr 10, 2013 19:41    Post subject: Re: Waterclear mineral from Nepal?  

Just to add a picture where can see vertical section of crystal shape.

Sorry if I'm completely wrong but in this matter my paper is as Devil's Advocate.



ab_GH17e.jpg
 Description:
Presumed albite/quartz
Ganesh Himal, Dhading District, Bagmati Zone, Nepal
crystal size: 8,1 x 4,3 x 1,3 cm
Photo & collection: Eric Manandhar

To my understanding, this is a view from c axis (almost). Look at the narrow face below with a sharp edge. Could be a prism face, edges are parallel, but angles with faces at right and left are never described in quartz (I think).

If it is quartz, largest face and shiny faces should be piramidal termination faces, but they are striated ...never seen in quartz.
 Viewed:  12936 Time(s)

ab_GH17e.jpg



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PostPosted: Apr 10, 2013 20:32    Post subject: Re: Waterclear mineral from Nepal?  

Based on Josele's most recent image, here is an attempt to interpret this crystal as quartz. This is very preliminary and hangs primarily on the proposed identifications of the forms along the left side.

I had a challenge to save this image - it was too large for a screen capture, but I was able to extract it from the web pages. However, the aspect ratio changed significantly in the process. I used Photoshop to try to get the proportions about right, but the image may be a bit distorted relative to Josele's.



quartz puzzle.jpg
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 Viewed:  12925 Time(s)

quartz puzzle.jpg



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PostPosted: Apr 11, 2013 15:52    Post subject: Re: Waterclear mineral from Nepal?  

It's a pitty that was me and not Pete or other expert who casually had this specimen in hand in Kathmandu.
Only thing I can do is try to explain that I remember:
- A section of the crystal perpendicular to elongated direction is something like an asymmetrical rhomb, with some bevels.
- Parallel edges with different angles between faces are parallel to elongated direction.
- Larger faces between these parallel edges are very striated.

I can not find any evidence of trigonal symetry and many of mono or triclinic systems.



ab2.jpg
 Description:
In both sides of the crystal there is striation parallel to edges and to elongated direction.
Because of the shape crystal, I only can see one posibility for c axis: parallel to elongated direction and also to edges and to striation.
 Viewed:  12812 Time(s)

ab2.jpg



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PostPosted: Apr 11, 2013 15:57    Post subject: Re: Waterclear mineral from Nepal?  

I suspect we will get to the bottom of this eventually but in the meantime it is an amazing crystal no matter what flavor.
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PostPosted: Apr 14, 2013 18:59    Post subject: Re: Waterclear mineral from Nepal?  

After spent much time (I am too headstrong) thinking about Pete Richards last post with interpretation of faces and also Peter Slootweg c axis scheme and unique crystal hypotesis in Mindat, I begin to understand this crystal as quartz.

Thanks to all for your help, I learned a lot with your inputs, and special thanks to Jordi who since the beginning proposed quartz for this crystal.



RIMG0529.JPG
 Description:
Here can see a larger part of quartz matrix, whose c axis direction seems the same as proposed for Pete Richards and Peter Slootweg and points to a unique crystalline building.
 Viewed:  12619 Time(s)

RIMG0529.JPG



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