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 Post subject: Re: The Ugly
PostPosted: Wed Nov 17, 2010 11:55 pm 
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RI wrong for spodumene
garnet is cubic therefore not pleochroic
RI wrong for axinite

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Is the RI between 1.60-1.69?

No


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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 1:49 am 
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I'm gettin desperate but....but...

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Quote:
Is the RI between 1.7 and 1.8?

Yes.


:?:
Can't we pretend?....Meh, ok, go back to sleep, yup, got that wrong for Ax.

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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 3:19 am 
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Is it a pyroxene?
Is it diopside?

edit: heh missed the RI and page 2 totally :oops:

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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 5:47 am 
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epidote ?

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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 6:59 am 
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Let's go for the composition:

Contains Si?
Contains Al?

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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 7:58 am 
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Quote:
epidote ?


YES!!!


The specimen was identified through the following data:

Origin: Pyrenees mountains, south of France
Associated minerals (in the same pocket): quartz crystals (strangely shaped), iron oxydes or hydroxydes, and what I think is actinolite (emerald green fibers).
Crystals shape: prismatic, some suggesting monoclinic system
Visible cleavage on /001/
Hardness greater than 6 and no greater than 7
SG: 3,38 to 3,39
Color: olive greenish-brown
Streak: white
Polariscope: 1/4 rotation (anisotropic)
RI: n1:1,715 n2:1,726 n3:1,735
Birefringence: 0,020
Optical sign: biaxial negative
Stongly trichroic: dark green/ yellowish-green/ greenish brown
Diffraction grating spectroscope: one strong absorption line in the right of the blue.

These crystals sure arn't pretty, but have some good size (the biggest is 6cm), so I will have so search for more in the same area, and maybe I could find better quality ones.


Last edited by cascaillou on Thu Nov 18, 2010 6:59 pm, edited 1 time in total.

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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 11:31 am 
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Congrats marcm. Good powers of elimination.
And for your reward, cascaillou promises not to send you the specimen. :wink:

I liked this quiz. =D> =D> =D>


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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 11:52 am 
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And for your reward, cascaillou promises not to send you the specimen

hahaha sure. He would have to content himself with a gigantic wall-size free poster of this beauty :lol:


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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 12:03 pm 
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Thank you, Barbra.
I'm used to play this kind of quizzes on this (french) forum : http://gemminquiz.forums-free.com/
Thanks, Cascaillou for the poster :lol:

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 Post subject: Re: The Ugly
PostPosted: Thu Nov 18, 2010 12:38 pm 
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It is interesting to note than when you have a greenish to brownish or brownish to black prismatic crystal, likely candidates are among the following:

-epidote group minerals
-pyroxene group minerals
-amphibole group minrals
-enstatite group minerals
-tourmaline group minerals
-vesuvianite group minerals
-kornerupine-prismatine series

Stick to the most significative minerals of each of these groups, leaving aside the obscure stuff, then proceed by elimination.


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 Post subject: Re: The Ugly
PostPosted: Fri Nov 19, 2010 2:35 am 
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I did look like an epidote specimen I have. Although mine is a much cleaner :D

Too bad somebody guessed before I saw this topic :(

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