FMF - Friends of Minerals Forum, discussion and message board

[Mark Ost]

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.

[Josele]

[Pete Richards]

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!

[Josele]

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.

[Pete Modreski]

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.

[Josele]

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.

[Pete Richards]

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.

[Josele]

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.

[Mark Ost]

I suspect we will get to the bottom of this eventually but in the meantime it is an amazing crystal no matter what flavor.

[Josele]

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.