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PostPosted: Mon Oct 13, 2008 3:31 pm 
What colouring elements are there for natural blue spinel?


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PostPosted: Mon Oct 13, 2008 3:38 pm 
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very rarely cobalt and more often ferrous iron (Fe2+)

Looks like you can send of that list to a publisher when you're done ;) It seems to cover a whole lot of info :smt023


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PostPosted: Mon Oct 13, 2008 3:56 pm 
How ace is spinel?

What other gem material makes it so damn clear when it's synthetic? Tabby effects, differing colouring elements (spectrums) and even a variation in RI and SG. And the most desired/valuable colour can not even occur as a synthetic. The blue makes itself pretty well known on the CCF too.

Added to that the lack of any property weaknesses - lack of cleavage, hard, lustre. Good colours.

It's in the cubic crystal system - so no messing around with birefringence values, dichroscopes and conoscopes. Finally it occurs, of course, in the beautifully simple octahedral state - none of this icositetrahedral nonsense.

Raise a glass to spinel - keeping gemmology simple


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PostPosted: Mon Oct 13, 2008 4:10 pm 
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not very relevant to the above but there is a slight connection...

http://www.burmarubies.com/RubySpl.html


:shock: I've got to see that piece myself before I'm a believer!


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PostPosted: Mon Oct 13, 2008 4:17 pm 
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:shock: :shock: :shock: :shock:

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PostPosted: Tue Oct 14, 2008 9:41 am 
CCF?:

Blue: Apatite, Tanzanite, Kyanite, Iolite

Green: Nephrite, Apatite, Bowenite

Since apatite is coloured be R.E. elements, does that mean it won't show anything in CCF? Or have I missed the point (never been sure about what the CCF fundementally does tbh - test for chromium and cobalt?)

Is blue zircon colour centres like blue topaz?


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PostPosted: Tue Oct 14, 2008 10:00 am 
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I checked my little (3mm) "neon" blue apatites under the Chelsea and they were inert. Of course, perhaps they're just too small to show much of anything :-k :lol: .


Kyriakin -- I have a list of Chelsea filter reactions ... if you'd like, I can PM it to you.

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PostPosted: Tue Oct 14, 2008 10:10 am 
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We have a list of Chelsea Filter reactions posted here:
http://gemologyonline.com/chelsea_filter.html

Please remember Chelsea Filter reactions will NOT identify anything; at best, they may eliminate a possibility.


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PostPosted: Tue Oct 14, 2008 10:13 am 
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Okay ... that's the one, Barbra! I think Snizzy put it together :D .

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PostPosted: Tue Oct 14, 2008 10:55 am 
It's main results are:

aqua/topaz/spinel and synemerald/emerald/paste?

Still unsure why jadeite would be green as it is coloured by chromium :?

Edit: 'green' in the chelsea colour filter


Last edited by Kyriakin on Tue Oct 14, 2008 6:59 pm, edited 1 time in total.

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PostPosted: Tue Oct 14, 2008 11:50 am 
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The color one observes with a "color filter" is a result of the transmission spectrum of the filter, the transmission spectrum of the sample, and the quality of one's eye sight.

I have written a small 30 page booklet, "Gemstone Characterization Using Hanneman Filters" which is included in my filter sets. (You can obtain a copy for $2 postpaid.) The booklet contains the transmission spectra of my filters and also that of the Chelsea Filter.


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PostPosted: Tue Oct 14, 2008 5:36 pm 
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Hi

As to your question still unsure why jadeite is green if colored by chromium?

lots of green gemstones are colored by chromium , jadeite , alexandrite , some emerald, chrome tourmaline , (grossular, diopside,enstatite)
but it also can produce red in some gemstone too, like ruby, pink saphire ,red spinel .

as to why , is if its an allochromatic gemstone or an idiochromatic gemstone

read more here:
http://gemologyproject.com/wiki/index.p ... s_of_color

hope this helps :wink:


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PostPosted: Tue Oct 14, 2008 6:32 pm 
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Can anyone explain how the ruby in the link provided by Spauwe crystallized in that shape? I am admittedly pretty ignorant when it comes to crystallography, but that thing really confuses me.

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PostPosted: Tue Oct 14, 2008 6:53 pm 
dragonstek wrote:
Hi

As to your question still unsure why jadeite is green if colored by chromium?

lots of green gemstones are colored by chromium , jadeite , alexandrite , some emerald, chrome tourmaline , (grossular, diopside,enstatite)
but it also can produce red in some gemstone too, like ruby, pink saphire ,red spinel .

as to why , is if its an allochromatic gemstone or an idiochromatic gemstone

read more here:
http://gemologyproject.com/wiki/index.p ... s_of_color

hope this helps :wink:


lol, I meant 'green' through CCF.

If I didnt know chromium could cause green colours, I think I'd have quit the FGA by now lol

I thought chromium generally caused a red colour under CCF?


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PostPosted: Tue Oct 14, 2008 7:04 pm 
allen wrote:
Can anyone explain how the ruby in the link provided by Spauwe crystallized in that shape? I am admittedly pretty ignorant when it comes to crystallography, but that thing really confuses me.


Thought it was a red diamond. Delusions of grandeur...


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