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 Post subject: Another Chatoyant Mystery
PostPosted: Sat Jul 01, 2006 11:21 pm 
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I am usually just a mere constituent of a gem that has been revered for over 3000 years.
I am cool as a cucumber on my own!
:twisted: Nothing, and I mean nothing :evil: , can get me fired up!


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PostPosted: Sun Jul 02, 2006 9:41 am 
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A popsickle?


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PostPosted: Sun Jul 02, 2006 10:56 am 
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\:D/ Great guess, Doos, but incorrect. [-X
Additional Hints: My color can vary from dark green to light green due to the presence of ferrous iron. I have 2 directions of cleavage and I'm a softy at heart, but tough when I need to be.
I'm not proud of it, but I am a member of a group. I often stand out because of an absorption line at 503nm.
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:-k

PS. Does it look like I'm trying to show off the new smilies in the View More Emoticon Section? 8-[ I'm Shameless. [-(


Last edited by Barbra Voltaire, FGG on Sun Jul 02, 2006 3:54 pm, edited 2 times in total.

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PostPosted: Sun Jul 02, 2006 1:22 pm 
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I'll try kornerupine.


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PostPosted: Sun Jul 02, 2006 1:50 pm 
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Sorry, cmw [-X
Another clue:
The group that our mystery stone belongs to is arbitrarily defined by the amount of iron present. Isomorphic replacement of iron and magnesium.
Habit: Aggregates of long, often fibrous (or asbestiform :idea: ) prismatic crystals
:wink: This clue should be a slam dunk!


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PostPosted: Sun Jul 02, 2006 1:55 pm 
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Barbra wrote:
Isomorphic replacement of iron and magnesium.
Habit: Aggregates of long, often fibrous (or asbestiform prismatic crystals


I've been thinking actinolite, an amphibole, but your spectrum info doesn't fit any source I have on hand. I'll still go with it, though.


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PostPosted: Sun Jul 02, 2006 2:04 pm 
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=D> We have a winner =D>
It is a cabochon of chatoyant actinolite that was sold to me years ago as chatoyant nephrite.
Actinolite is considered a primary constituent of nephrite.
It has a hardness of 5.5 although it's fibrous structure, when chatoyant, makes it a toughie.
It is a member of the Actinolite-Tremolite series, classified as amphibole inosilicates, a series that also includes nephrite.
Its long fibrous crystals can be spun into fireproofing asbestos.


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PostPosted: Sun Jul 02, 2006 2:37 pm 
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:?: Where do your spectrum data come from Barbra? :?: (See, I'm getting on board) :!:

I checked Anderson & Payne and they describe a vague band in the yellow of "undetermined wavelength," and two faint and narrow bands at 510 and 495 nm.

They add this interesting info: "Actinolite can be thought of itself as a true jade, since 'nephrite' is merely the term for a massive amphibole of the tremolite-actinolite series. 'Mutton-fat' nephrite is almost entirely iron-free tremolite, while the commoner green nephrite contains iron and is nearer to actinolite in composition. In recent years actinolite cat's-eyes from Taiwan have been sold as nephrite cat's-eyes." So maybe your stone is really nephrite :D

Somewhere over the years I've also heard that chatoyant actinolite also comes from the huge nephrite deposits in Alaska.


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PostPosted: Sun Jul 02, 2006 2:57 pm 
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The inspiration for the spectrum is courtesy of
Tables of Gemstone Identification or
Bestimmungstabellan fur Edelstein Synthesen Imitationen Mit Farbigen Spektren Zweisprachig
by Birgit Gunther (although the spectrum is a PhotoShop mock-up)
The 503nm reference is also in Gems by Webster. It is also almost identical to the spectrum my actinolite cab, pictured above, displays with my OPL.

I am speculating that the difference between nephrite and the more common actinolite is structural. As I recall, nephrite has an alpha helix atomic structure (with a much finer grain), which makes it harder and much tougher than commonly fibrous and granular actinolite. And, I don't believe nephrite is used for the production of asbestos.

But, I could be wrong. :-k


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