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 Post subject: Possible ID for turquoise-blue cab?
PostPosted: Mon Oct 26, 2009 2:43 am 
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I bought this cab about 15 yrs ago at a bead show. I'd planned an intricate design for it, but life got in the way ;-) & I never used it. Flash forward to a few weeks ago when I came across it again; I can't do the kind of work I used to do (waah!) so I thought I'd sell it on ebay. Only problem is I can't remember what this stone is, & I'm a total ignoramus about ID tests. I doubt I paid more than $15 or at the most $20 for this, so I'm thinking this isn't especially rare.

I'd bought a chrysocolla cab at the same time as this & thought this was one too, but when I looked online it didn't look like any chrysocolla I could find photos of. I just now turned the stone over though, & noticed a bit of dark green mottling & tiny dark green dots each surrounded by faint darker blue shapes. So maybe chysocolla after all?

Image

The color's just a hint lighter & slightly more green, so the stone's a rich turquoise-blue. It's not just highly polished, but also a bit more translucent than the photo shows. I know it's not possible to I.D. a stone w/100% accuracy from a photo, but given that, any educated guesses?

Also, any unobtrustive tests I can do that will give me better info? I don't know if this is an appropriate question, but here goes: what might you expect to pay for this?

Thanks!
Hamsa


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PostPosted: Mon Oct 26, 2009 9:13 am 
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:) hi hamsa, and welcome to the forum!! whatever the cabochon may be, it is a beautiful color! our gemmo experts will tell you that it is not possible to id a stone by photographs alone, and i'm not an expert but it does look like chrysocolla.

i read one site that says chrysocolla will stick to your tongue. also read that chrysocolla can be scratched easily-hardness of 2.5-3.5.

here's some interesting information you may enjoy reading: (don't represent this site)
http://www.cst.cmich.edu/users/dietr1rv/Default.htm


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PostPosted: Mon Oct 26, 2009 11:27 am 
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Variscite? Pics look more green than blue....??? That's about all you'll get from pics is total guesses so please don't name your stone because one of us said it "looks like xxxx".....

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PostPosted: Mon Oct 26, 2009 11:55 am 
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I wouldn't recommend putting copper bearing minerals in your mouth.

Chyrsocolla is often associated with other copper bearing minerals such as malachite and azurite.
I have a few cabs with several tones of blue and green in them that are combos of all three.

Do a little research on Eilat Stone (the National stone of Israel).


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 Post subject: Possible ID for turquoise blue cab
PostPosted: Tue May 11, 2010 12:24 am 
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hello there,

I am curious to know how do we separate the color between Indicolite tourmaline vs. paraiba tourmaline. How can we tell if a paraiba tourmaline is copper bearing ? is there a test to it or just by the color?

Indicolite color description is violetish blue, greenish blue similar to paraiba color description how do we separate the two?

Thanks for any information or links

Cheers
sera


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PostPosted: Tue May 11, 2010 2:30 am 
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If hardness is high, "Gem silica" crosses my mind...

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 Post subject: Re: Possible ID for turquoise blue cab
PostPosted: Tue May 11, 2010 3:18 am 
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Hi Sera and welcome to the forum, :D

telamarie wrote:
How can we tell if a paraiba tourmaline is copper bearing ? is there a test to it or just by the color?


Copper bearing tourmalines exhibits a peak in the absorption spectra around 700 nm caused by Cu2+, you must have access to at least a VIS-NIR spectrometer to spot it. There's a nice article in the G&G, spring 2008.
hope that this helps.

ciao
alberto

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PostPosted: Tue May 11, 2010 9:43 am 
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Just a quick note... the primary diagnostic peak is at 900nm. Copper and iron both produce a peak at 700nm.


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PostPosted: Tue May 11, 2010 9:48 am 
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yups, correct, Dr. Brian....

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