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Unknown alteration from Kipawa,Quebec

Posted by Reiner Mielke  
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Reiner Mielke December 04, 2018 08:43PM
I shouldn't be asking this but thought it might be fun to see what comes of it.
The sample is from here:https://www.mindat.org/loc-614.html

It appears to be a layer of brown Hiortdahite II in eudialyte with a white alteration layer on top. The white mineral looks somewhat fibrous but it difficult to tell as it is so fine grained. The white unknown is soft <3 but it is not possible to say if that is due to the cohesion of the fibrous crystals or the crystals. The thickness of the white layer is 2-3mm and the unaltered Hiortdahlite II layer 0.5-1cm. The white layer fluoresces pale turquoise under LW and the Hiortdahlite II layer reddish pink.
Here are some photos:






Edited 3 time(s). Last edit at 12/04/2018 09:08PM by Reiner Mielke.
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Reiner Mielke December 04, 2018 08:53PM
More pictures and EDS results, the last EDS is of a Hiortdahlite II sample posted by Pavel on Mindat for comparison. My sample appears to lack Na but the system used under reports Na ( and over reports Ca) . It is possible that it contains no sodium in which case I do not know what it is. However it's fluorescent response is typical for hiortdahite II from there.






Edited 1 time(s). Last edit at 12/04/2018 08:58PM by Reiner Mielke.
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Paul Brandes December 04, 2018 08:53PM
Have you had it analysed yet, Reiner?

Edit: strike the above comment! ;-)



Edited 1 time(s). Last edit at 12/04/2018 08:55PM by Paul Brandes.
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W. Richard Gunter December 04, 2018 09:02PM
Hi Reiner:

It may be a mixture of gittinsite and another phase. Gittinsite is a white alteration product and your "unaltered" trace has calcium-zirconium-silicon which is should. The fluorescence of gittinsite at Strange Lake is bright orange in SW but I don't know what it is at Kipawa.
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Reiner Mielke December 04, 2018 10:28PM
Gittinsite certainly seems to be the most likely thing.
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Pavel Kartashov December 05, 2018 08:28PM
Zr:Si ratio in the alteration product is higher than in both zircon or gittinsite. And Ca peaks are too low for gittinsite also.
I am suppose here mixture at least of three phases, one of which is some calcian zeolite. Two other are zircon and free zirconia (may be ZrO2*nH2O).
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Reiner Mielke December 05, 2018 11:32PM
You are correct Pavel, Ca is much too low for gittinsite. I will dissolve some in acid and see what I get. If there is a zeolite it should dissolve. Actually the Zr:Si ratio of zircon Zr(SiO4) is 1:1 which this what this appears to be so that is a possibility. However I find it difficult to imagine zircon being an alteration product. Is free zirconia a mineral? I will also try a different hardness test by grinding some between two sheets of glass, If there is zircon it should scratch the glass.



Edited 1 time(s). Last edit at 12/05/2018 11:33PM by Reiner Mielke.
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Alfredo Petrov December 05, 2018 11:43PM
Remember that SEM/EDS isn't quantitative and is least quantitative for the light elements like Na, Si...
so I wouldn't trust that for determining Zr:Si
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Reiner Mielke December 05, 2018 11:50PM
It effervesced in HCl a little bit so the Ca is probably from calcite. Most of it does not appear to be soluble but it is too early to say for sure. Between two sheets of glass it easily turned to powder and I did not observe any scratches but that may be that it is so fine grained that I could not see the scratches. I will let you know what the final acid test results are. It looks like I will have to get powder XRD done on it.
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W. Richard Gunter December 05, 2018 11:59PM
You might get baddeleyite (ZrO2) in there. At Strange Lake we did not get baddeleyite; the calcian elpidite altered to gittinsite and late-stage zircon. Unusually the late-stage zircon did not fluoresce in SW UV but the gittinsite did.
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Reiner Mielke December 05, 2018 11:59PM
Hello Alfredo

For two closely spaced peaks like that in that range it is close to the true ratio. There is only a problem when you are trying to compare peaks a relatively great distance apart, like the Si and Ca peaks. In this case Ca is greatly over reported so there is actually less Ca than the peak indicates. However like you say for light elements like Na there is a serious problem, in this case Na is grossly under reported and anything lighter than Na cannot even be detected with this setup. Either way I doubt I will be able to determine what this is without XRD. Also some of the Al may be contamination from the chamber so that cannot be quantified except to say ( because of the size of the peak) in this case Al is present.



Edited 1 time(s). Last edit at 12/06/2018 12:02AM by Reiner Mielke.
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Pavel Kartashov December 06, 2018 12:19AM
Compare intensities of Si and Zr in EDX spectrum of zircon with your spectrum.
EDX spectrum of high-hafnian Zircon from Viitaniemi.

Viitaniemi pegmatite, Eräjärvi area, Orivesi, Pirkanmaa, Finland

Remember that you should to extract some Si (approximately equal to Al) for zeolite. So Zr:Si ratio here in reality is even more than it is visible from the first sight.
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Reiner Mielke December 06, 2018 12:32AM
Hello Pavel,

I see what you mean but I do not know if Kerry's result is precise enough to rule out zircon. Here is an EDS by Kerry for zircon done a few years ago when he had a different detector so I don't know if it is directly comparable. However that pattern is similar to the unknown. I will get XRD done in a few weeks that should provide some answers.

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Pavel Kartashov December 06, 2018 12:36AM
Alfredo, when you constantly works with different zirconosilicates, you may approximately to recognize Zr:Si ratio (for example in row zircon-gittinsite/catapleyite-wadeite-elpidite).

Richard, you should to remember, that Strange Lake is granite, while Kipawa is nepheline-syenites with less abundance of silicon. Baddeleyite impossible in granite, but quite possible in syenites (especially alkaline and melanocratic).

I am think, that it don't manage without zeolite here, may be sodian.
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Pavel Kartashov December 06, 2018 12:41AM
Any analyst accustoms to his own detector... I unable to judge about one of Kerry. It looks like his detector understating Si systematically.
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Reiner Mielke December 06, 2018 12:48AM
Hello Pavel,

I agree that his old detector was under reporting Si. I do not know about his new one. I will ask him if he has results for Zircon that he got with his new detector.
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W. Richard Gunter December 06, 2018 03:39PM
Hi Pavel:

I agree about baddeleyite at Strange Lake yet there was enough silica at both Strange Lake and Kipawa to form gittinsite.
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Reiner Mielke December 07, 2018 08:09PM
Except for a bit of carbonate the remainder is insoluble in HCl. Also Kerry's new detector gives the same results as his old one so it looks like his system favours Zr over Si.

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