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 Post subject: AQUA VS GOSHENITE?
PostPosted: Wed Jul 16, 2008 11:20 pm 
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Hello! Thanks for all the help on garnets everyone!

Where do you draw the line on Pale Aqua vs Goshenite?

Is it as easy as, "don't see any color, Goshenite?" Even light color Aqua?

Thanks!


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PostPosted: Thu Jul 17, 2008 3:54 am 
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yep, that would be it...


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 Post subject: Aqua vs Goshenite?
PostPosted: Thu Jul 17, 2008 10:10 am 
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GEE WHIZ!! Something easy in the gemstone world????

Thank you so much for your answer Spauwe!


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PostPosted: Thu Jul 17, 2008 10:52 am 
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Spauwe is correct (as usual).
Goshenite is colorless....if it's not colorless, it's not goshenite.


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PostPosted: Thu Jul 17, 2008 12:17 pm 
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Can't it still be, mineralogically speaking, Aquamarine instead of Goshenite even if the eye can't see any blue? Wouldn't the presence of Fe2+ make it Aqua, even if there's so little as to make it "effectively" colorless?


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PostPosted: Thu Jul 17, 2008 12:46 pm 
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gem-n00b wrote:
Wouldn't the presence of Fe2+ make it Aqua, even if there's so little as to make it "effectively" colorless?


That is like saying the presence of chromium ion makes it emerald, even if so little is present the material remains colorless to the eye. What if it contains equivalent nanoscopic amounts of both chromium and iron?!

If it is colorless to your eye, then the amount of iron and/or chromium ion is below the detection limit of your eye. So call it goshenite.


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PostPosted: Thu Jul 17, 2008 12:57 pm 
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You can call it what you like, but if you are paying your own money for a goshenite, I would suggest you test it with one of my Aqua-filters. "If it's aquamarine, you'll see green." If its goshenite, you won't.


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PostPosted: Thu Jul 17, 2008 1:24 pm 
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I use the chelsea filter for Aqua, and see green, is that good enough?

Or do I need a different filter?


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PostPosted: Thu Jul 17, 2008 1:39 pm 
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I'm not saying it'd make sense to value it as Aqua (either for buying or selling), that's why I made it clear that the domain in which I was inquiring was mineralogical. My query was as to whether it is mineralogically proper to refer to a pale Aqua as a Goshenite. In other words, can it be Goshenite if there are any iron impurities?


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PostPosted: Thu Jul 17, 2008 5:01 pm 
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gem-n00b wrote:
I'm not saying it'd make sense to value it as Aqua (either for buying or selling), that's why I made it clear that the domain in which I was inquiring was mineralogical. My query was as to whether it is mineralogically proper to refer to a pale Aqua as a Goshenite. In other words, can it be Goshenite if there are any iron impurities?


Well, when I took my mineralogy courses (mmmmph) years ago, there was no such distinction made. Beryl was Be3Al2(Si6O18). Varieties were distinguished by color, and that was that. There was no "pink emerald" "white aquamarine", or anything of the sort. Emerald was defined as the green variety of beryl, Morganite as the pink variety, etc. (Don't even get me started on "green amethyst"...:smt013 )

To put my 2 cents in on your comment above (from a mineralogical standpoint...), I think it comes down to definitions. Goshenite is, by definition, colorless beryl. If it's blue, it's aqua. The impurities cause the color, of course, but I don't think they were or are the basis for the definitions. They're simply impurities.

Now, if someone's changed the definitions in the past (mmph...) years, then all bets are off....

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PostPosted: Thu Jul 17, 2008 6:30 pm 
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I agree with Kevin. There is a big difference between gem classifications in the fields of Gemology and Mineralogy. I had a recent conversation with Dr. Andrew Christy, of the ANU Geo-Science Lab regarding the presence of trace elements that cause colouration. It is not an Aquamarine unless the colour manifests in the stone. You have to remember that in Africa many dealers think Goshenite is Aquamarine as long as it came out of an Aqua Deposit!

A Geologist or Mineralogist will then defer to a Gemmo on the Optical Properties of the stone. The Mineralogist may say 'this is blue gem-grade corundum' as opposed to 'this is a nice ceylon blue sapphire'.

I have some Orange/Yellow 'Usambara Effect' sapphires that change from Golden Orange outdoors or in Natural light, to Ruby Red in weak or artificial light. By virtue of their Chromium content theoretically they should be blood red, but because they have nickel acting as a masking agent they are not. Even though they change colour to red, no-one is game to call them a ruby and the final classification re gem status is left to Gemmos (many of whom are still scratching their heads over these stones). Hence, as HME rightly stated
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The impurities cause the color, of course, but I don't think they were or are the basis for the definitions. They're simply impurities.


No blue = No Aquamarine.


Paul

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PostPosted: Thu Jul 17, 2008 7:41 pm 
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From the structural crystallography point of view there's only "beryl". :smt024


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PostPosted: Fri Jul 18, 2008 2:43 am 
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HME wrote:
....Emerald was defined as the green variety of beryl, Morganite as the pink variety, etc....it comes down to definitions. Goshenite is, by definition, colorless beryl.... Now, if someone's changed the definitions in the past (mmph...) years, then all bets are off....


To keep my sanity, I have to agree with this. There are people out there insistently making distinctions between green beryl and emerald, and for all I know they may be right. There are a lot of aquas out there with a decidedly greenish tint, too.For my money, the green ones are emerald, and if you want me to call it aquamarine, I had better be able to see some blue in there.

I have some beryls that were sold to me as morganites, and some others that were cut from rough that I can guarantee was aqua, but they are so pale the cut stones don't show color. That makes them goshenites now.

Albert Einstein is credited with saying, "Things are as simple as they can be, but no simpler." The corollary would be, "Don't make things more complicated than necessary."

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PostPosted: Fri Jul 18, 2008 9:44 am 
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Ok, now I have another question?

I see "green" beryl advertised alot........ But they look nothing like Emeralds.

They are a light, green, almost like Prasiolite and CLEAN..... So are they just poor quality Emeralds?

Or is there really a niche for "green beryl" that is not Emerald?


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PostPosted: Fri Jul 18, 2008 5:14 pm 
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Hi Breeze,

Maybe I'll just confuse you further but let me tell you how the Gemmological Association of great Britain deals with this.

Emerald is green beryl coloured by chromium.

Aquamarine (either green or blue though lots/most of the blue ones are produced by heating green stones) are coloured by Iron in one valence state or another

Green beryl is coloured by vanadium

The Gem-A were so serious about this that back in the 1920's or 30's they developed the chelsea colour filter to seperate the chromium stones from the pretenders...ignoring the fact that a well saturated vanadium stone was far superior to a weakly saturated chromium stone...then...

...sometimes long ago in a galaxy far far away (I think the sixties though I'd have to look it up to be sure) The GIA certified a nice well saturated emerald green coloured stone which owed it's colouring to vanadium instead of chromium as an emerald. This opened a whole can of worms, though the GIA being a commercial concern wasn't worried about that...It just wanted to make money. Suddenly it was possible to get your vanadium coloured beryls certified as emeralds and so everyone who had access to these beautiful stones were posting them off to the GIA who would, without so much as a blush, send you back a certificate with the word 'EMERALD' stamped in large bold font.

So whose right and whose wrong???...Dunno the answer to that one. I'm just an old cynic that doesn't trust large educational establishments...commercial enterprises posing as educational establishments...banks...insurance companies...corporations etc etc etc

So if your buying a peelie wallie light green stone then insist it's a green beryl...If your selling the same stone then insist it's an emerald (especially if it's got a chromium spectrum)

Or you could just give an honest unbiased description of the stone and hang all the marketing jargon.

I don't know how our discipline is ever going to be taken seriously as a science as long as we allow ourselves to bow to marketing mumbo jumbo profit. greed, misrepresentation and downright fraud...

...But it's never boring :D

Be well...best wishes from an old cynic

Frank


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