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Kipawa Thorite

Posted by Reiner Mielke  
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Reiner Mielke September 25, 2009 12:19PM
I have several specimens from Kipawa that look very similiar to: http://www.mindat.org/photo-191604.html
However mine fluoresce a strong bright green in short and longwave UV. They are also strongly radioactive and tan to brown with a conchoidal fracture and in long crystals with a square cross-section. If not for the fluorescence I would have called it thorite. Opal is reported from that occurrence and I am thinking that what I have is opal pseudomorph thorite. My question is, "is the thorite in the mindat photo fluorescent? " I am thinking that maybe all the thorite from that place has been replaced by silica.
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Reiner Mielke September 27, 2009 12:05AM
Pictures of one of the samples. In this particular sample the "Thorite" is associated with Agrellite. Other samples are with Eudyalite and or Magnesiokataphorite. Size if sample is 7cm X 6cm
open | download - Thorite.jpg (804.9 KB)
open | download - Thorite Fluorescence.jpg (703.2 KB)
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Matt Neuzil September 27, 2009 04:16AM
Could it possibly just be a coating that is on your thorites?

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A buena hambre no hay pan duro
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Michael J. Bainbridge September 27, 2009 01:23PM
It's my understanding that the thorite from Kipawa is fluorescent. I'll check with the guy who's got the claim and let you know.
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Rob Woodside September 27, 2009 03:49PM
The Thorites I saw in CMN basement in Ottawa and like a damn fool declined were quite dark brown in colour. Does mossandrite fluoresce?
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László Horváth September 27, 2009 04:26PM
The fluorescent mineral is a Th-bearing phase possibly something like thornasite, which is fluorescent. As far as I know thornasite has not been reliably confirmed, but the chemistry of the fluorescent phase points in that direction.
Laszlo
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Reiner Mielke September 27, 2009 06:31PM
Thank you everyone for your input and suggestions, much appreciated.
The fluorescence is not a coating, if you break one of the xls up the fluorescence is throughout. I have had a closer look with a UV pointer and some areas of some xls and some xls do not fluoresce at all. The non-fluorescent sections and xls tend to be are darker brown and some are dark brown. Although I have one that does not fluoresce and it is yellow-brown to tan just like the ones that do fluoresce! I am assuming that the non-fluorescent ones are unaltered thorite. Some crystals are completely fluorescent, I am assuming they are completely altered.
Thornasite is a possibility but the colour doesn't match but that wouldn't be the first time a colour doesn't match. Anyone want some to play with? I have lots.
Mosandrite does not fluoresce and has a different luster ( glassy v. wazy )
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Pavel Kartashov September 27, 2009 08:26PM
Such colour of fluorescention is usual for uranyl carbonates and for uranyl ion adsorbed on silica (difference in brightness exist between them - carbonates usually more bright).
Thorite itself usualy is nonfluorescent, but some metamict thorites don't containing Fe may be fluorescent in such colour, because any thorite contain some uranium.
Mosandrite usualy contain Th>>U, so it is nonfluorescent.
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Tim Jokela Jr September 28, 2009 12:14AM
Hey Laszlo, wasn't somebody going to write up Kipawa a while back? Fascinating locality, needs to be published.

T
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László Horváth September 28, 2009 12:29PM
Tim
I have heard such rumors for the last 10 years but they are probably groundless.
Laszlo
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Michael J. Bainbridge September 28, 2009 01:18PM
Well, it sounds like everyone's already got it all figured out but I just heard back from Darryl. Here's what he says:

"Thorite, calcite and sometimes gittinsite from Kipawa all fluoresce green under SW UV light. They can be recognized from each other in visible light. The thorite occurs as tan-coloured blocky grains and fluoresces an
intense lime-green colour. It is also very radioactive. The calcite occurs as a coating on fracture surfaces and so is more spread out, and fluoresces less bright than the thorite. I've never seen the green fluorescent gittinsite but the National reported that it exists? Gittinsite is powdery-white in visible light and is often associated with vlasovite as they are end members of a solid solution series."

A little off topic, but I can confirm the fluorescence of the gittinsite - greenish white under LW and bright green in SW. Looks like a whitish rind on vlasovite in visible light. I have photos of this in one of the CMN specimens, when I get a chance to upload them I'll let you all know here.

Cheers,
Michael



Edited 1 time(s). Last edit at 09/28/2009 01:39PM by Michael Bainbridge.
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Reiner Mielke September 28, 2009 01:56PM
Hello Michael,

Thank you Michael. My Thorite samples fluoresce bright green in long and short wave UV. Here is the catch, some fluoresces and some doesn't. Some of the crystals have non-fluorescent areas in them, some crystals in the same sample fluoresce, and some don't. I am proposing that the fluorescent areas and crystals are altered to fluorescent opal and the non-fluorescent ones are unaltered. Any disagreement?

Reiner

PS. The gittinsite and vlasovite fluoresce under short wave as you noted.
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Michael J. Bainbridge September 29, 2009 02:52AM
Opal ps. thorite? Is that possible?
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Pavel Kartashov September 29, 2009 08:34AM
Mikhael,
What is metamict thorite from your point of view? It is mixture of amorphous silica (~opal) and thorianite. ;)
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Michael J. Bainbridge September 29, 2009 02:00PM
No no, I don't mean to disagree. I freely admit I don't know anywhere near enough to be in a position to do so. I've just never heard of it before, and based on what has been discussed here, I'm just not sure why that is the likely answer - or even if we've positively ascertained enough yet to draw any conclusion. If indeed that is the reasonable assumption, however, I'm curious to know more about it.

I know a little knowledge is a dangerous thing - and again, keeping in mind that I'm looking to be educated, not to challenge anyone - but based on what I understand, and what's been discussed here, these are my thoughts:

1. If opal is the inevitable metamiction product of thorite, then so be it, but given Darryl's assertion that the thorite fluoresces, and knowing that opal does not always do so; couldn't it be that the fluorescent part is the thorite, and the non-fluorescent part the opal?
2. That having been said, isn't opal by definition hydrated amorphous silica? Where does the water come from in this equation?
3. If the only reason we're discussing opal, however, is the mention on the mindat Kipawa page, then I would point out there is no reference given, or description of its occurrence. Is it known here as an alteration product of the thorite? Is it known to fluoresce at this location?
4. It seems to me too that there are other possibilities based on what has been discussed so far:
a) If Laszlo has reason to believe that it could be thornasite (which he says is fluorescent), why was that possibility dismissed?
b) Couldn't the fluorescence be caused by minute inclusions - in uneven distribution - of some other known fluorescent, like the calcite?
c) Or, couldn't it even be something else entirely?

I just don't see how any conclusions can be drawn yet. If it is based on some piece of knowledge which hasn't been mentioned because it has been assumed to be universally understood, could someone please enlighten me (or point me in the right direction)? Otherwise, unless someone has some other information that is directly on point and definitive, it seems to me that tests will be required to conclude anything.

Or there may be a very simple answer to my long-winded post, which I'm looking forward to.

Bottom line: This has been an intriguing and informative discussion about a very interesting location which I hope continues, and ultimately encourages someone to do a proper study so we can all know for sure.

Thanks,
Michael
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Reiner Mielke September 29, 2009 07:58PM
Hello Michael,

If you go to page 17 in : Publication No: ARV65-06
Publication Title: Radioactive mineral occurrences in the Bancroft area
Author: J. Satterly,D.F. Hewitt
Publisher: Ontario Ministry of Northern Development and Mines, Ontario Geological Survey
Publication Date: 1957
Publication Series: Annual Report Volume
Location: 31C,31D,31E,31F,Ontario, Canada

They mention thorite from the Kemp property that has altered to Silica, in essence Opal. Also in that same article it talks about uranothorite ( a variety of thorite) that is metamict to silica and thorianite. Opal associated with uranium is very commonly fluorescent but thorite is not. In fact I can't find any literature that says unaltered thorite is fluorescent, hence the pseudomorph theory. Water would simply be surface water.
I suppose it might be thornasite but it has never been identified from Kipawa.Wish it were thornasite, much sexier than opal. However based on what is known about thorite alteration and opal it is most likely opal after thorite.

Reiner
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Reiner Mielke September 29, 2009 08:30PM
Michael,

As far a opal is concerned check out : http://hal.archives-ouvertes.fr/docs/00/32/38/85/PDF/PL02078.pdf. In it they state "Not all opals are fluorescent, and two types of luminescence have been recognized. The first has a green color, is attributed to uranyl groups (Fritsch et al., 2001,2003) and is believed to be typical of common opals." etc.

Reiner
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Michael J. Bainbridge September 29, 2009 09:26PM
Well okay... that is pretty convincing. Thanks for taking the time to clarify, Reiner.

I'm secretly keeping my fingers crossed for sexy thornasite for you though!
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Michael J. Bainbridge October 01, 2009 11:18PM
Hey all,

Just to let you know I've posted the vlasovite & gittinsite photos I mentioned.

http://www.mindat.org/photo-254380.html
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Pavel Kartashov October 01, 2009 11:55PM
Mikhael, great photos and great specimen! thumbs upthumbs upthumbs up

I am don't know Kola assemblage wich can be comparable with this. May be only best specimens of parakeldyshite/eudialyte intergrowth from Umbozerskii Mine. Occasionally fluorescention of parakeldyshite also is green and similar to gittinsite one of your specimen.

Unfortunately Mongolian gittinsite don't fluorescent at all. It is strange, but on whole Khaldzan Buragtag massif only K-feldspars, zircons and willemite has fluorescention.
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Michael J. Bainbridge October 02, 2009 03:07AM
Thanks Pavel! I think I have a few others you may like. Let me see what I can dig up.
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Maggie Wilson October 02, 2009 11:39AM
http://www.mindat.org/photo-254565.html

Here's some from Reiner's trip this summer. I just uploaded them this morning, so the child photos may be a while appearing.
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Michael J. Bainbridge October 02, 2009 01:26PM
Nice, that's a great little combination piece!
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Reiner Mielke October 04, 2009 12:29PM
Hello Everyone.

Thanks to Laslo's suggestion of Thornasite there has appeared a new twist. I thought I would try to determine if the samples where opal or Thornasite by placing a piece in HCl. Opal is insoluble in HCl but I thought Thornasite might be soluble with release of silica gel much like many of the other silicates at Kipawa. Much to my surprise it turns out that it is neither! The sample began to bubble and dissolve leaving behind a hard white porous mass that did not fluoresce nor was it radioactive. However the acid was radioactive indicating that the thorium and/ or uranium where leached from the sample.
The only uranium carbonate that I know of that fluoresces green under LW & SW is Liebigite but I know of no Thorium carbonates that fluoresce. Any suggestions to what the mineral that dissolved might be?
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pharos July 11, 2012 05:42PM
What about calcite + thorite ? or calcite + opal pseudomorph thorite as you said.
Calcite take thorium element when you put it on hcl, and your porous mass is silica from "opal"
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