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Green Tourmaline... no chrome in it, but really bright
https://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=6&t=23827
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Author:  Luca [ Thu Jul 13, 2017 11:21 am ]
Post subject:  Green Tourmaline... no chrome in it, but really bright

Dear friends,
I have bought this green tourmaline from Namibia
its about 1 carat, well cut in stepped octagon.
The color is intense green, with a hint of yellow. It does not turn red under Chelsea filter, thus no chrome is in this stone.
I wonder whether such a bright green is due to iron. I know, in fact, that green tourmalines are often colored by iron, but this one is particularly vivid.
here some pics
Image
Image
Image
Image

Thank you for all the replies
:D :D :D

Author:  Barbra Voltaire, FGG [ Thu Jul 13, 2017 12:43 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really brigh

Tourmaline can have so many variables when it comes to the transition metal impurities which cause color.
Fabulous color!

http://www.elementsmagazine.org/archive ... zzotta.pdf

Author:  Marlow [ Thu Jul 13, 2017 1:40 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really brigh

Like it very much! Great color...

Found this bright 2,20 ct in St Marie aux Mines.

Sold as a "Merelani" Diopside - the dichroism was to strong and I liked it very much so I took it. With a little hope that it could be a bright green kornerupine too. At the moment they offer some.

So "only" tourmaline - orign unknown - maybe Mozambique ( dealer is specialized in Tanzania gems ) or another african source.

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Eyeclean with very nice cutting.

Author:  Stephen Challener [ Thu Jul 13, 2017 3:12 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really brigh

The stone in the original post looks nice but also typical of tourmaline? Maybe it's just my monitor but I don't see anything that makes me think it wouldn't be iron colored, it's just a nice example.

Author:  Luca [ Fri Jul 14, 2017 3:29 am ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

@Barbra thank you for the suggested reading :D
It is really interesting!!!

@Marlow I really like your tourmaline with this nice mint color... :D I think this particolar hue is rare in a tourmaline.

@Stephen Maybe my tourmaline is colored by iron. However, it seems to me different from other tourmalines I have seen before. So, I supposed that this bright green might be due to a different element.
I have read that some green tourmalines (with no red reaction at the Chelsea filter) are colored by vanadium.

Author:  Seaglow [ Fri Jul 14, 2017 2:18 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

Small stones and the bigger one is included but nice color. Nigerian origin. 0.75ct. and 1.19 cts.

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Author:  Luca [ Sat Jul 15, 2017 5:11 am ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

@Seaglow
Very nice stones! :D

Author:  Seaglow [ Sat Jul 15, 2017 6:59 am ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

Luca, no red fluorescence, so most likely vanadium.

Author:  ruby302 [ Tue Jul 18, 2017 4:37 am ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

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Ive posted this pic before because this is chrome tourmaline, african origin & is not readily easy to come by even on the webs, it will change to a reddish color under a chelsea filter & will also change under incandescent light, the chrome content is so high in these stones- 8)

Author:  Barbra Voltaire, FGG [ Tue Jul 18, 2017 2:07 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

Everyone who has followed my posts over time knows that simply being colored by a specific elemental chromophore does not guarantee beauty.

Modifiers like copper, chromium, are often used as hype to promote gems which would be hard to sell otherwise.

Author:  ruby302 [ Tue Jul 18, 2017 2:53 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

If i may please add-maybe not beautiful, but unique for what they are, nature adds true gems to the menu & variety to see-Ive seen some unique gems in the last few months that were not seen before or were not known of, so to speak- :?: 8)

Author:  Marlow [ Tue Jul 18, 2017 4:16 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

Well, sometime they are not "beautiful" but really interesting....

2,58 ct UE Tourmaline...

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LED - quite close to daylight color which is a bit better and cooler green.

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Incandescent light - both pics

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Author:  maialetto [ Tue Jul 18, 2017 4:52 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

I have one of those large UE chrome tourmalines as well. It's one of my favorite stones, I admit, but from an aesthetic point of view is so dark that under "normal" illumination is almost black.

Only with strong illumination I get bright green and red sparkle. :) Really beautiful, but if I were to choose a stone to wear, that's just too dark. I'm always tempted to recut it, but I'm sure it won't improve it much, if at all, so I have to live with it...

Author:  Marlow [ Tue Jul 18, 2017 11:36 pm ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

Fortunately my stones is not to dark and custom cut ( Coast to Coast ).

A friend of mine, Uli Zeisberg, bought nice CC garnet rough with a visible usambara effect - first time I could see it in garnet. Greyish green bodycolor in daylight but the thicker part in the middle was greyish pink. Can't wait to see the cut stone.

Author:  Luca [ Sun Jul 23, 2017 9:55 am ]
Post subject:  Re: Green Tourmaline... no chrome in it, but really bright

Thank you all for the replies,
I definitely agree with Barbra that one specific chromophore (Cr, Vn, Cu) doesn't necessarily confer beauty to a stone.
However, it seems to me that the trade market does take this aspect in great consideration.
In particular, in my old edition (2015) of the Gem Guide, green tourmaline under 1 ct is valued 25-40 dollars for the fine quality and 40-60 dollars for the extrafine quality.
BTW, I have paid my tourmaline more than 60 dollars per carat (no matter since I liked the color).
On the other side, in the Guide chrome tourmaline is valued much more (125-250 dollars per carat for the extrafine quality).
Thus, it seems that the presence or the absence of a specific chromophore is more important than beauty to estimate the value of a gem?
Why?
thank you
:D :D :D :D

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